Add link to icon font in Iconography section

[asibilia]

Note: for support questions, please use one of these channels: Chat: BullhornOSS Gitter

I'm submitting a ...

• bug report
• feature request
• question about the decisions made in the repository

What is the current behavior?

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via

https://plnkr.co or similar. (TODO - make a starter plnkr)

What is the expected behavior?

What is the motivation / use case for changing the behavior?

Please tell us about your environment:

• Angular version: 2.0.0-beta.X
• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

Other information

(e.g. detailed explanation, screenshots, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, gitter, etc)