Replace Path with AsRef<Path> in Watcher functions

[frangio]

This should be a non-breaking change and it removes the need to call Path::new when calling watch or unwatch. This means watcher.watch("/tmp/foo") is now valid.

[passcod]

I've wondered how to do that... thank you very much for this :)
Add yourself to the Cargo.toml and I'll get this merged.

[frangio]

No problem :)

[frangio]

Hmm, I just realized that by removing the & now the methods are taking ownership of the argument when they really shouldn't. Give me a moment to sort it out.

[frangio]

That should be it.

[passcod]

Awesome :) I'll merge after work

[frangio]

@passcod, sorry to bring this up again, but I think I was wrong with the last change I made (commit bb3c978). The method signature before that was better and is consistent with the Rust standard library. See for example http://doc.rust-lang.org/std/fs/struct.File.html#method.open. As for my concern regarding moving/borrowing, it's not a problem at all since the argument passed can still be a reference.

So I think commit bb3c978 should be reverted.

[passcod]

Done in 3340d74.