Fixed and polished version of PR https://github.com/gorakhargosh/watchdog/pull/133

The SkipRepeatsQueue is directly cherry-picked from the pull request, I actually hit this also on Linux as well with a very fast rename test. (the commit seems to indicate it's a Windows only issue, that's not the case, the order of events is meaningful in all platforms)

The FixDirectorySnapshot is almost the same as in the PR except we no longer make an extraneous FileDeleted/DirDeleted events for renamed files/dirs. This brings the behavior in line with the rest of Watchdog.

Tested on OS X 10.8 and Ubuntu Linux 12.10.