Push rejected failed to detect set buildpack heroku/ruby - ruby

Question

I'm attempting to add the following project to my slack chat "https://github.com/PDaily/lita-destiny" I have added the lita integration on my slack chat. I've made a new app on the heroku site, I've added to the global config vars, my LITA_TOKEN, GITHUB_URL and by BUNGIE_API_KEY. I've used cmd and the heroku toolkit and logged in to heroku. I've then changed directory to where the lita-destiny folder is located. I've then done
Bundle install
Git add.
Git add -u
Git commit -m "heroku"
Git push heroku master.
I've installed all the native gems, also in the root of that folder is a gemfile.
However I get the error in the title there. I've also performed
heroku buildpacks:set heroku/ruby
2016-03-31T00:14:25+00:00 app[heroku-redis]: source=REDIS sample#active-connections=1 sample#load-avg-1m=0.33 sample#load-avg-5m=0.24 sample#load-avg-15m=0.215 sample#read-iops=0 sample#write-iops=0 sample#memory-total=15405632.0kB sample#memory-free=13328628.0kB sample#memory-cached=482376kB sample#memory-redis=294048bytes sample#hit-rate=1 sample#evicted-keys=0
2016-03-31T00:15:24+00:00 app[heroku-redis]: source=REDIS sample#active-connections=1 sample#load-avg-1m=0.255 sample#load-avg-5m=0.235 sample#load-avg-15m=0.215 sample#read-iops=0 sample#write-iops=0 sample#memory-total=15405632.0kB sample#memory-free=13328504.0kB sample#memory-cached=482372kB sample#memory-redis=294048bytes sample#hit-rate=1 sample#evicted-keys=0
2016-03-31T00:16:48.562723+00:00 heroku[api]: Release v12 created by munkeyboy14#gmail.com
2016-03-31T00:16:48.562723+00:00 heroku[api]: Deploy 97376bc by munkeyboy14#gmail.com
2016-03-31T00:16:48.723963+00:00 heroku[slug-compiler]: Slug compilation started
2016-03-31T00:16:48.723974+00:00 heroku[slug-compiler]: Slug compilation finished
2016-03-31T00:16:48.698905+00:00 heroku[web.1]: State changed from crashed to starting
2016-03-31T00:16:48+00:00 app[heroku-redis]: source=REDIS sample#active-connections=1 sample#load-avg-1m=0.22 sample#load-avg-5m=0.24 sample#load-avg-15m=0.22 sample#read-iops=0 sample#write-iops=0 sample#memory-total=15405632.0kB sample#memory-free=13328232.0kB sample#memory-cached=482380kB sample#memory-redis=294048bytes sample#hit-rate=1 sample#evicted-keys=0
2016-03-31T00:16:50.125875+00:00 heroku[web.1]: Starting process with command `bundle exec lita`
2016-03-31T00:16:52.409755+00:00 app[web.1]: /app/vendor/bundle/ruby/2.2.0/gems/lita-slack-1.7.2/lib/lita/adapters/slack/api.rb:63:in `call_api': Slack API call to rtm.start returned an error: invalid_auth. (RuntimeError)
2016-03-31T00:16:52.409772+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-slack-1.7.2/lib/lita/adapters/slack/api.rb:38:in `rtm_start'
2016-03-31T00:16:52.409773+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-slack-1.7.2/lib/lita/adapters/slack/rtm_connection.rb:20:in `build'
2016-03-31T00:16:52.409774+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-slack-1.7.2/lib/lita/adapters/slack.rb:22:in `run'
2016-03-31T00:16:52.409774+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-4.7.0/lib/lita/robot.rb:80:in `run'
2016-03-31T00:16:52.409775+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-4.7.0/lib/lita.rb:80:in `run'
2016-03-31T00:16:52.409776+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-4.7.0/lib/lita/cli.rb:77:in `start'
2016-03-31T00:16:52.409778+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/thor-0.19.1/lib/thor/command.rb:27:in `run'
2016-03-31T00:16:52.409778+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/thor-0.19.1/lib/thor/invocation.rb:126:in `invoke_command'
2016-03-31T00:16:52.409779+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/thor-0.19.1/lib/thor.rb:359:in `dispatch'
2016-03-31T00:16:52.409780+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/thor-0.19.1/lib/thor/base.rb:440:in `start'
2016-03-31T00:16:52.409800+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/bin/lita:23:in `load'
2016-03-31T00:16:52.409782+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/gems/lita-4.7.0/bin/lita:6:in `<top (required)>'
2016-03-31T00:16:52.409800+00:00 app[web.1]: from /app/vendor/bundle/ruby/2.2.0/bin/lita:23:in `<main>'
2016-03-31T00:16:53.126028+00:00 heroku[web.1]: Process exited with status 1
2016-03-31T00:16:53.137278+00:00 heroku[web.1]: State changed from starting to crashed
above is the latest error message from heroku logs

Answer 1

If I am understanding your question correctly, there is a fundamental misunderstanding about how lita works. The lita gem has an executable (lita new) that creates a new lita bot for you. You then add plugins like lita-destiny to the Gemfile of your lita bot.
So you are getting this error because you are not pushing code that Heroku recognizes as a Ruby app-- you are pushing a gem.
What you should do is
cd ../some/place/else
gem install lita
lita new
cd lita
echo 'web: bundle exec lita' >> Procfile
bundle install
git init
git add .
git commit -m 'Initial commit'
heroku apps:create
git push heroku master
Then you can add the lita-destiny plugin to the Gemfile of your lita bot (the project you just created above) and add config.handlers.destiny_handler.api_key = 'XXXX' to the lita_config.rb file in that same project. You also add your Slack API Key to the lita_config.rb file.
Source: lita docs and heroku docs