Issue/3268 Add dark tab bar

Code for [Google Code Issue 3268](https://code.google.com/p/iterm2/issues/detail?id=3268).
Let's keep the open brace at the beginning of a method on the same line as the method name, e.g.
- (NSString *)name {

I've been slowly migrating to this new style and I want to keep new code using it.