Remove less.js-windows submodule.

Will replace it in next commit with a release version.
Add release version 1.5.0 of less.js-windows.
Update base template to include Atom feed link instead of RSS.
Update bundled libs and use new version of HTML5 Boilerplate.

normalize.css is also now bundled and available for themes to use.
Updates for theme compatibility with upcoming Bootswatch themes.
fix slug processing to allow for numeric tags

It appears that the YAML parsing is smart enough to see that something that is entirely numeric should be a number. For example:

    Tags:
    - 2013
    - 2014

However, the slugify method assumed that the `text` being passed to it was actually text. In these cases, it could be an `int` which caused `engineer build` to fail. By casting `text` to `unicode` we avoid this problem.
Merge pull request #80 from pridkett/patch-1

Fix slug processing to allow for numeric tags.
Ensure tags are unicode strings in all cases and add numeric tag test

Related to #80 - prior to this tags were always whatever type they were
parsed as by the YAML parser.

After this change they’ll always be unicode when accessed through the
`Post.tags` property. The `_tags` property will still contain the raw
parsed types from the PyYAML in case those are needed for some reason
in the future.

Side effect of this change: numeric tags (or any tag that would be
parsed as anything other than a unicode string) will be persisted in
the post source file as an explicit string type by the Metadata
finalization plugin. For example, a post with metadata like this:

    tags:
    - 2013

Will be rewritten as:

    tags:
    - ‘2013’
OUTPUT_DIR_IGNORE should ignore .gitignore files by default.
Fixes #77.
Initial attempt to fix #82.
More complete fix for #82.

Ignored paths should now be handled properly both in the clean command
and in the mirror_folder function.

One edge case exists: mirror_folder will delete an orphan folder even if it is ignored
if it contains no files. This is noted in the OUTPUT_DIR_IGNORE documentation.
Merge remote-tracking branch 'github/dev' into dev
Merge master branch changes into dev branch
Fix lazy link unit tests that were failing on Windows.