travis: Move to Ubuntu Trusty image
travis: Move to Ubuntu Trusty image

fedelibre/hugo,mdhender/hugo,mdhender/hugo,gohugoio/hugo,mdhender/hugo,fedelibre/hugo,mdhender/hugo,fedelibre/hugo,anthonyfok/hugo,anthonyfok/hugo,gohugoio/hugo,anthonyfok/hugo,gohugoio/hugo,fedelibre/hugo