Add dark weather plugin

I needed to setDrawsBackground:NO on the web view, which makes for better looking plugins in both dark and light mode.

Changed the padding in the weather plugin so it is a little more like other Spotlight panes.

Added dark weather plugin:

![screen shot 2014-11-12 at 09 43 21](https://cloud.githubusercontent.com/assets/28582/5007352/7f45f7b6-6a50-11e4-946c-85122fd7092b.png)