Squashed 'vendor/rack-pjax/' changes from 67e7b60..092530e

092530e Release 0.7.0

git-subtree-dir: vendor/rack-pjax
git-subtree-split: 092530ef80e62fa880db898fa22b9658a7a4fd25
Merge commit 'b1f69947c879eba306d790bb7c654c52cbb843ef' into sample-app
Vendor rack-pjax 0.7.0
Using jquery.pjax version v1.2.0
Add Procfile for heroku