Add support for OUTPUT_DIR_IGNORE setting.

Fixes issue #66.
PEP8 changes.
Fix up PyCharm inspection/style settings and fix some minor formatting issues.
Add .gitattributes for line ending normalization.

Unfortunately there are some files that aren't properly normalized
in the repo for whatever reason, so this commit is ugly. Hopefully this
resolves the issue for the future.
Remove Tweet submodule.
Remove Tweet-related settings and theme content.

Fixes #65.
Switch to less.js-windows instead of dotLESS.

dotLESS seems to be buggy, especially when using lots of
nested @import statements.
Cache the results of LESS file compilation.

Should speed up builds with complex LESS file substantially.
Add setting to force metadata fencing for all posts.
Update default permalink style to 'pretty'.

Fixes #31.
Fix minor formatting issue in docs.
Add documentation for handle_settings method.
Support path expansion in settings which contain paths.

Fixes #74.
Handle missing post directories.

Fixes #73.
PEP8 formatting cleanup.

Fixes #64.
Remove unneeded backup file from PyCharm project version upgrade.
Add Global Links plugin.
Merge experimental/replace_dotless
Update less.js-windows.
Fix cache invalidation problems.