solarize color theme better supported

This modification should make the colors match up more closely with those using a Solarized scheme.  See http://ethanschoonover.com/solarized for more details.

Before (note the colored background behind .vimrc and vim-7.4.tar.bz2)
![dircolors-before](https://f.cloud.github.com/assets/1007405/2516013/5493544a-b449-11e3-9bea-1d836e79766b.png)

After (note the 'clear' background)
![dircolors-after](https://f.cloud.github.com/assets/1007405/2516016/6080aa64-b449-11e3-9f3f-376d202efd43.png)