Use app_BRANCH env var as GitHub branch to deploy on Heroku (default to master if env var does not exist)
+ fix use of branch to monitor
Make master the default GitHub branch to pull and push
Add test for a push on a branch different from monitored one
Add test for a push on the monitored branch
Add 2 tests for HerokuDeployer with a monitored GitHub branch, used to fetch/reset & push
Merge pull request #8 from lyontechhub/master

Use app_BRANCH env var as GitHub branch to deploy on Heroku