Merge pull request #31 from Ledej/multiple-environments-support

Support multiple heroku environments
Support before/after deploy scripts
Add before/after event log
Fix the heroku command by adding the heroku app name
Use a better command output
Fix the log
Fix again the logging
Add the heroku gem to have access to the command heroku
updates from heroku devcenter article

https://devcenter.heroku.com/articles/rails-unicorn
Merge pull request #32 from ZeroFucks/unicorn-updates

updates from heroku devcenter article
environment and ref are first class in deployment models now
Merge pull request #33 from ZeroFucks/update-payloads

environment and ref are first class in deployment models now
nuke unused method, thanks @foca
Support before/after deploy scripts
Add before/after event log
Fix the heroku command by adding the heroku app name
Use a better command output
Fix the log
Fix again the logging
Support pre/post deploy scripts to wrap the execute method