More pathogen/vundle friendly

[kevinjqiu]

Honour the vim folder structure by putting the colorscheme file in colors/ folder, so pathogen (vundle or anything that manipulates the runtime path) can pick up the color scheme.

[slix]

There's some discussion about this in #5.

If using git submodules, there's a way to make it work well with pathogen, but I'm not sure about vundle.