support main branch in Circle config
support main branch in Circle config

Reviewed By: vrama628

Differential Revision: D30016328

fbshipit-source-id: 0149f7a8c69ba799b318bb9942acf8e3f8dbe113

mroch/flow,mroch/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,facebook/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,facebook/flow,facebook/flow