much needed documentation

[tippfehlr]

This theme is awesome, but for a lot of features I need to go digging in the theme’s hugo templates.
It would be nice to have (unified!) documentation for things
like the complete front matter supported. (I just found out cover and coverCaption exists).

Also I adjusted the theme’s colors by copying _variables.scss to assets/scss/, it would be nice to describe that somewhere.

[rhazdon]

Hey @tippfehlr, you are totaly right! :D I will try my best to add some in a near future! :)