WIP: Adds features that encourage collaboration in plugin development

Work in progress.

Goals:
 - Warn users about potentially outdated plugins
 - Encourage users to participate in plugin development
 - Find new authors for abandoned plugin projects

Fixes #66 and #74

![plugin_page](https://cloud.githubusercontent.com/assets/883920/4682518/d00de204-561d-11e4-84f7-9ea72abb2460.png)

@PerJensen Any ideas how to make this look prettier? :)