Include names of committers in HipChat notifications

HipChat notification messages now say which committers were responsible, e.g.

Job patchelf:trunk:tarball: Failed, probably due to 2 commits by Eelco Dolstra

Created by  Eelco Dolstra  on July 2, 2013
NB2VOKIROXTIIIXKPHFHCGO236KPKXWYDSWUWVJF3XBRHRMUIQ4AC
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