Mime guessing doesn't work for shebang using /usr/bin/env

[Tim Hatch]

For files without an extension in the mime map, the guessing code looks for a line like

#!/usr/bin/python

This works great except for a lot of scripts these days (such as our own post commit hook) use

#!/usr/bin/env python

I propose making a reasonably trivial change to get_mimetype() that will make it recognize this syntax.

While I'm in there tweaking stuff, I'd also like to support some more vim-isms in modelines, such as filetype= and modelines near the bottom of the file (:help modelines reports that the first or last 5 are checked by default).

Thoughts?

[Tim Hatch]

Working version against r5883, for review

[Tim Hatch]

Fixed in r5889