patchinfo.vim: 'Gist' depends of 'WebAPI'
Add vtd to list of sources
Clarify README wording

I managed to get confused about which repository to use.
The new wording is unambiguous.
Merged in mackwic/vim-pi/mackwic/patchinfovim-gist-depends-of-webapi-1390404168862 (pull request #1)

patchinfo.vim: 'Gist' depends of 'WebAPI'
Merged in chogg/vim-pi (pull request #2)

Add vtd to sources and clarify README
Cron job update