Prevent formatting TinyMCE plugins from loading if scripts are missing

Refs #227
Add better attachment ID detection function to logo class
Customizer: fix missing font family options

Ensure that font family selects have been rendered before the JS tries
to populate them.
Remove whitespace in entry-date markup

Refs #228
Remove unnecessary color picker parameter

In WP < 4.1 the parameter is ignored, and in 4.1+ it breaks the picker.
Update changelog for 1.4.6
Update Google Fonts list and subsets
Bump version to 1.4.6
Merge branch 'release-1.4.6' into develop
Version 1.4.6