Revamped solarized theme again. Now much closer to solarized2.

This is a start towards a unified solarized theme. Most of solarized2's features have been brought over.

This patch brings:
- Better text contrast.
- More easily identifiable mode indicator/outer segment background colors.
- Darker gutter, making the mode indicator the most visually significant section.
- Refactored source. Much easier to tweak values in future.
- Compliance with updates to theme format.

![solarized2merge](https://f.cloud.github.com/assets/378622/792585/7180c3e4-eba9-11e2-9674-e9d068f6fa9f.png)