Suggestion to add bootswatch styles

Thanks for this project, I love how easy it was to deploy.

One of my concerns with bootstrap-saas is how inflexible it is. Yes, we can override styles in the bootstrap_and_overrides.css.scss file. The issue is that this file could become very messy if the project were being scaled and required a lot of customizations. A necessary evil? Perhaps...

My suggestion would be to offer a pre-built-in setup option to import styles from http://bootswatch.com/

This is just a thought for a future version, or if someone wants to fork it.