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 - Warn users about potentially outdated plugins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

![warning](https://cloud.githubusercontent.com/assets/883920/4902955/2651321a-643d-11e4-9e1f-bb7343b859c3.png)
![request](https://cloud.githubusercontent.com/assets/883920/4902954/264bf868-643d-11e4-8ff8-c8fbfa91ea16.png)
![manage](https://cloud.githubusercontent.com/assets/883920/4902953/2647fa1a-643d-11e4-9f43-ee7336c2e50a.png)