Shinyswatch

Other changes

* Use external images for README.md so that PyPI can render them. (ff23b59)

Other changes

* Update README.md

New features

* `theme` module contains 25 theme methods that wrap `get_theme()`. (4)

* Generic `get_theme()` method returns an HTML Dependency that overwrites the default `bootstrap` theme with the `bootswatch` theme. The returned HTML Dependency requires internet to load fonts. (4)