Also calling watchFile on collect, so that initially cached files get watched.

[wnr]

Fixes issue #306.

Calling watchFile in collect should not be a problem because 1) watchFile is smart enough to not add a file watcher if the given file is already watched and 2) collect is not executed often enough to impose a problem for the extra basic operations.

I noticed no performance difference watching my projects, and the test suite is running as fast as before:

before: npm test 5.63s user 0.88s system 25% cpu 25.075 total after: npm test 5.60s user 0.87s system 25% cpu 25.032 total