Fix bug where searching would trigger documentation view.

This is a slight hack, but I can't find any way to directly ask Sublime
if the user's input is currently in a search bar.

I also changed the function from on_selection_modified_async to
on_modified_async, because this function is only called when the user
types in something. Previously, the function would be called even if the
user moved the selection around with the arrow keys without typing.
Fix bug with documentation.

Unfortunately, calling sel() on active_view() will just return the same
object every time, so the comparison I was doing would always fail.
There's no easy way to compare sel() objects - you'd have to loop
through every selection to ensure it's right, and it gets even more
painful to duplicate - so I decided to check if the first region has
changed to see if we're typing in the find window or not.

If the user is actually using multiple selections, it's fine,
since it's hard to say which of the functions they're selecting should
be shown documentation anyways.
Ensure we're in a Haxe file.
Merge pull request #116 from johnfn/master

Fix bug where searching would trigger documentation view.