Feature: Add links to gem's homepage, source code, and documentation if they exist.

I added code to pull the gem's homepage, source code, and documentation urls from rubygems.org if they exist and display them using icons from ionic framework in a new column in the table.  

I found myself pulling up homepages to read the changelogs of my out of date gems.  This should make that easier.

![links](https://f.cloud.github.com/assets/16705/2176534/6d87145a-95d6-11e3-8ced-91e1414f5321.png)