Don't import watchdog outside of autoreload codepath

Watchdog throws an exception on import on PyPy on OS X.  As far as I can tell, it's because of this PyPy bug:

https://bugs.pypy.org/issue1166

Until that's fixed, I'm fine living without autoreload, but the current management command imports watchdog regardless of whether or not autoreload is being run.  This PR moves the import into the autoreload handler to avoid that issue (and bumps the version).