Don't run Travis against gh-pages branch
Don't run Travis against gh-pages branch

We don't have any testing infrastructure for GitHub Pages, so when Travis tries
to run `rake`, it fails.

muthhus/griddler,joeadcock/griddler,ValiMail/griddler,seanscal/griddler,thoughtbot/griddler,RubyDaily/griddler,joeadcock/griddler,joeadcock/griddler,firepoint/griddler,danavery/griddler,danavery/griddler,firepoint/griddler,ValiMail/griddler,Inchdev/griddler,pipefy/griddler,muthhus/griddler,vahtel/griddler,firepoint/griddler,Inchdev/griddler,seanscal/griddler,Inchdev/griddler,ValiMail/griddler,wingrunr21/griddler,r38y/griddler,danavery/griddler,r38y/griddler,muthhus/griddler,vahtel/griddler,pipefy/griddler,seanscal/griddler,RubyDaily/griddler,wingrunr21/griddler,thoughtbot/griddler,vahtel/griddler,RubyDaily/griddler,wingrunr21/griddler,r38y/griddler,pipefy/griddler,thoughtbot/griddler