Update gems and add a few for development
Add Guardfile for better testing
Move application.css to application.css.scss

For better control over stylesheets, use the
SCSS style over the Rails manifest style for
importing styles, especially for bootstrap.
Updating categories

* Use Bootstrap styles for category management
* Add basic feature request for creating a category
* Do not use category/show for now. Kinda empty and boring
Pretty print slim output in development
Add new feature specs for category management
Make sure features work with multiple categories
Updating page headers for categories
Add navbar for basic navigation in posts