Fix google preview image classes for fonts with space in name
Ugly, but all previews working!
Change name to Styles Font Menu
Merge branch 'develop' into f/previews

Conflicts:
	classes/styles-font-menu.php
Convert font arrays to font classes
Rename all the things
Fix @imports
Rename to group and single, because google came before group
Generate standard CSS from class.
Move inline styles to enqueued CSS
Move dropdown.php to menu.php
Change readme header
Add prefix to Google classes
Remove ineffective height declaration
Rename class in comment
Fix image preview generation.
Move SFM_Image_Preview init into SFM_Image_Preview class
Move font variant logic to font class from previews
Move font variant info into font class
Previews class paired down. Font methods moved to font class. Resolves #3.