Refactor findExports a little
Refactor findExports a little

I'm about to add support for exports on a reassigned `exports` object.
Before I do that, I wanted to make the methods a little more structured
and take option objects instead of just a list of arguments. This should
make the new addition a little simpler.

trotzig/import-js,Galooshi/import-js,trotzig/import-js,trotzig/import-js