Update codeschool.vim

g:colors_name should point to a valid color scheme file.  Fixing.

`Error detected while processing /Applications/MacVim.app/Contents/Resources/vim/runtime/syntax/synload.vim:
line   19:
E185: Cannot find color scheme 'Code School 3'`
Merge pull request #34 from thebitguru/master

Fix an error in codeschool.vim