Add custom header for status updates.
Add custom header for status updates.

It's required to set the new context status attribute.

travis-ci/travis-core,developerfm/travis-core,Tiger66639/travis-core,jantman/travis-core,kidaa/travis-core,final-ci/travis-core,developerfm/travis-core,Tiger66639/travis-core,Tiger66639/travis-core,kidaa/travis-core,final-ci/travis-core,final-ci/travis-core,GistIcon/travis-core,jantman/travis-core,developerfm/travis-core,GistIcon/travis-core,kidaa/travis-core,travis-ci/travis-core,travis-ci/travis-core,GistIcon/travis-core