Number of tiny tweaks to v2

- Changed theme header text to “Choose a theme”
- Tweaked theme sub header text
- Added all 16 theme choices
- Tweaked color of social notice (we won’t post without permission)
- Moved close ‘x’ on modal to right.
- Changed color of modal toggle icon
Merge pull request #3 from Automattic/daves-v2-changes

Number of tiny tweaks to v2