Load custom fonts in the post editor

* Moves all font-related functions to functions/custom-fonts.php
* New function: cakifo_get_font_info() - get font name and weight from the handle
* New function: cakifo_editor_font_classes() Adds the font name and weight to the editor body class (used in later commit)

Thanks to @justintadlock for the help with enqueueing the fonts.
First pass at new editor styles
* Moved to css/editor-style.css
* Use Sass to generate the editor style. Sass makes it possible to loop through each custom font and font weight to automagicly
generate the CSS