Octopress Asset Pipeline gives errors when trying to build site - ruby

Question

I am trying to build my Jekyll site with Octopress 3. I wanted to use the Octopress Asset Pipeline plugin but I keep getting this error when I run jekyll build:
/usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:140: warning: already initialized constant Jekyll::PageHooks
/usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:140: warning: previous definition of PageHooks was here
Configuration file: /Users/robcrocombe/Documents/octopress/test/_config.yml
/usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset': stack level too deep (SystemStackError)
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:169:in `reset'
... 10066 levels...
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary.rb:19:in `program'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/bin/jekyll:17:in `<top (required)>'
from /usr/local/bin/jekyll:23:in `load'
from /usr/local/bin/jekyll:23:in `<main>'
I have tried with a clean installation using octopress new blog. I am running OSX Yosemite. Here is my Gemfile:
source "https://rubygems.org"
gem 'octopress', '~> 3.0'
group :jekyll_plugins do
gem 'jekyll-sitemap'
gem 'octopress-asset-pipeline'
end
When I remove 'octopress-asset-pipeline' it builds fine. What is going wrong? Thanks
EDIT: I have added 'octopress-hooks' to my Gemfile and I don't get that error anymore, instead I get this:
Configuration file: /Users/robcrocombe/Documents/octopress/test/_config.yml
Source: /Users/robcrocombe/Documents/octopress/test
Destination: /Users/robcrocombe/Documents/octopress/test/_site
Incremental build: disabled. Enable with --incremental
Generating...
Liquid Exception: no implicit conversion of nil into String in _posts/2015-10-28-welcome-to-jekyll.markdown
Liquid Exception: no implicit conversion of nil into String in _posts/2015-10-28-welcome-to-jekyll.markdown
/usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll.rb:157:in `expand_path': no implicit conversion of nil into String (TypeError)
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll.rb:157:in `sanitized_path'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:374:in `block in in_source_dir'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:373:in `each'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:373:in `reduce'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:373:in `in_source_dir'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/liquid_renderer.rb:16:in `file'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/renderer.rb:105:in `render_liquid'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:311:in `render_liquid'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/renderer.rb:60:in `run'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:306:in `run'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:171:in `block (2 levels) in render'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:169:in `each'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:169:in `block in render'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:168:in `each'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:168:in `render'
from /usr/local/lib/ruby/gems/2.2.0/gems/octopress-hooks-2.6.1/lib/octopress-hooks.rb:197:in `render'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/site.rb:59:in `process'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/command.rb:28:in `process_site'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/commands/build.rb:60:in `build'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/commands/build.rb:35:in `process'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/lib/jekyll/commands/serve.rb:26:in `block (2 levels) in init_with_program'
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `call'
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `block in execute'
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `each'
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `execute'
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/program.rb:42:in `go'
from /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary.rb:19:in `program'
from /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-3.0.0/bin/jekyll:17:in `<top (required)>'
from /usr/local/bin/jekyll:23:in `load'
from /usr/local/bin/jekyll:23:in `<main>'
The YAML front-matter of 'welcome to Jekyll' markdown file is:
---
layout: post
title: "Welcome to Jekyll!"
date: 2015-10-28 19:23:27 -0700
categories: jekyll update
---