Vim: set filetypes on .pryrc and Gruntfile automatically

This beats having to litter those files with `vim: ft=...` hints.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Vim: back out Gruntfile filetype detection

Gruntfiles are supposed to be named Gruntfile.js, so this isn't
necessary.

Signed-off-by: Wincent Colaiuta <win@wincent.com>