Fixes for new fsnotify

[mattn]

go.exp/fsnotify is too old

[rjeczalik]

Does it fix any particular problem beside being old? Could we add a test-case for that?

[mattn]

fsnotify seems have API compatibility without changing API names. But one thinng, the type of Events/Errors was changed. so we don't need to check whether the value is nil or not.

[mattn]

i.e. i guess no need to add tests.