Windows: Don't use os.path.join() for URL paths.
Windows: Use posixpath in nav.FC.make_absolute()

nav.FileContext.make_absolute() is only used to compare
links to entries in mkdocs.yml, so it makes sense for it
to only use POSIX-style paths.

Without this, the site fails to build because it checks for
a Windows-style path in a list of POSIX paths in
build.PathToURL.__call__().

This is the last change required to build the mkdocs site
on Windows.
Updated setup.py to use entry_points['console_scripts'] instead of scripts.

This makes a "mkdocs" command on Windows/OSX/Linux without any platform-specific code in setup.py.

I think this is the preferred way to install a Python command with setuptools.

It is, at least, the method used by:

* [flake8](https://bitbucket.org/tarek/flake8/src/8ee94d1eeea36e835583b68c59682bfc3684fab9/setup.py?at=default)
* [coverage.py](https://bitbucket.org/ned/coveragepy/src/ca875e739048c3b333e862471b89d55e3c7b7170/setup.py?at=default)
* [Fabric](https://github.com/fabric/fabric/blob/master/setup.py)
* Many others

In the past, I had to change imports willy-nilly or add
"from __future__ import absolute_imports" to a bunch of files.
This is because I was renaming "mkdocs" to "mkdocs.py" instead of "main.py",
and the module-vs-script name clash was confusing imports from other files.
flake8 fixes in main.py (How did this ever pass?)
Update the menu/toc to support the new nav code changes.

fixes gh-110
Merge pull request #122 from edbrannin/windows-command

Fix "mkdocs" command creation in Windows
Merge pull request #124 from ryanneufeld/fix-gh-110

Update the menu/toc to support the new nav code changes.
Merge pull request #121 from edbrannin/windows-paths

Fix path-handling on Windows
Improve whitespace around css and script tags
Remove reference to the `config` variable in the template files
Add support for extra_css and extra_javascript in all the themes
Avoid repeated overwrites of config['extra_*']

Fixes #133
Merge pull request #136 from jimporter/config-var

Remove reference to the `config` variable in the template files for custom themes
Merge pull request #90 from jimporter/extra-css

Add support for extra_css and extra_javascript in all the themes
Merge pull request #134 from dnrce/bug/133-wrong-extra-media-paths

Avoid repeated overwrites of config['extra_*']
Merge pull request #135 from dnrce/extra-media-whitespace

Improve whitespace around css and script tags
Use Tox to run the tests on Travis

Rather than repeating the steps in the Travis config, use Travis to run
tox. This has the added benifit of verifying the setup.py install into a
virtualenv.
Removed flake8 exclusion that wasn't needed