Hightlight line in textmate/sublime text for light themes

Hello,

This pull request fix the reported problem in the following issue: https://github.com/chriskempson/base16-textmate/issues/9

As you may want to check how the result looks, here are some screenshots for monokai, mocha and solarized themes :
![monokai](https://f.cloud.github.com/assets/752030/360899/9c2b5f58-a1af-11e2-8f23-d89ce9661559.png)
![mocha](https://f.cloud.github.com/assets/752030/360898/9c2cb128-a1af-11e2-8008-4aab64932292.png)
![solarized](https://f.cloud.github.com/assets/752030/360900/9c3c4b42-a1af-11e2-9fdb-520eeea3457a.png)