Allow CI failures for ruby-head
Allow CI failures for ruby-head

See: https://twitter.com/travisci/status/352451358563110915

odedniv/jbuilder,WellframeInc/jbuilder,nambrot/jbuilder,maclover7/jbuilder,rails/jbuilder,vincentwoo/jbuilder,suryasnath/Venture,ASnow/jbuilder,jasnow/jbuilder,sue445/jbuilder