Don't use pygmentize to highlight git's heads

[bernardobarreto]

Githat highlights this
diff --git a/Gemfile b/Gemfile index 5079908..1925a6a 100644 --- a/Gemfile +++ b/Gemfile
with diff lexer, but I still prefer the git's original highlight (bold white).

And for
@@ -1,3 +1,30 @@
use the original blue/green.

I think these colors are better, and it will probably take less time to highlight (I hope).