Add the homepage back to the navigation

Fixes #236
Use os.path.sep for Windows support

Fixes #238
Replace another slash I missed.
Added a test for the path handling and found a bug
Raise a configuration error for invalid pages configs
Fixed URL parse error when using GitHub Enterprise

GitHub Enterprise deployments are a little unpredictable and this patch removes an error when using `mkdocs gh-deploy`.  It also includes a few PEP8 cleanups.
Check for CNAME file when using gh-deploy

If a CNAME file exists in the gh-pages branch, we should read it and use that URL as the expected GitHub pages location.  For branches without a CNAME file, we will try to determine the URL using the origin URL.
Fix test failure

Caused by a change breaking a new test that had been sitting in a PR.
Catch errors in the Watchdog error handler

Fixes #164
Add a test for the strict mode and change to an exception rather than
assert