Adds 'Symbols' group with several new links

#### New links: 

**Fonts**
+ [Lost Type Co-Op](http://losttype.com/)

**Symbols**
+ [Font Awesome](http://fortawesome.github.io/Font-Awesome/)
+ [Entypo Pictogram Suite](http://www.entypo.com/)
+ [Symbolset](http://symbolset.com/)

**Colors**
+ [ColorZilla](http://www.colorzilla.com/)