Fix py3 empty string parsing.
Merge pull request #119 from ryan-roemer/bug-py3-support

BUG: Fix py3 empty string parsing for `theme_bootswatch_theme`
Reset navbar CSS and update history. Fixes: #114
Bump version to v0.4.4
Minor README fix.
Merge branch 'master' of https://github.com/EricFromCanada/sphinx-bootstrap-theme