Try to get current branch name

.travis.yml

@@ -49,6 +49,7 @@ notifications:
 # FIXME this needs refinement, obvs
 after_success:
   - "test $EMBER_VERSION == 'default' && test $TRAVIS_PULL_REQUEST && ember deploy prod --verbose >> deploy_output"
+  - git symbolic-ref HEAD | sed 's!refs\/heads\/!!'
   - "cat deploy_output"
   - "cat deploy_output | grep 'revision=' | cut -d '=' -f 2 >> index_key"
   - "cat index_key"