s:projectionist_detect: only handle .vim files

[blueyed]

This avoids sourcing the autoload file for scriptease#locate when not
editing Vim files.

The projectionist setup gets also done for doc/*.txt, which gets
skipped now. This could be changed/enhanced if needed.

[tpope]

That autoload is unfortunate, but I do want this for doc files, README files, Python files, everything really.

If this really is a pain point, I'd accept a bit of duplication. Maybe give scriptease#locate a second optional parameter for candidates, then duplicate just the candidate portion in the plugin file.

[blueyed]

Amended.
Also made it work for me after, by using resolve(): I have symlinks in my &rtp.

[XVilka]

@blueyed can you please rebase this one?

[tpope]

Remove the resolve() calls you tried to sneak in while you're at it. Make your case for that separately.