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

src/script/hydra-build

@@ -17,7 +17,7 @@ my $db = Hydra::Model::DB->new();
 
 my $config = getHydraConfig();
 
-my @plugins = Hydra::Plugin->plugins(db => $db, config => $config);
+my @plugins = Hydra::Plugin->instantiate(db => $db, config => $config);
 
 
 sub addBuildStepOutputs {