Performance

Hi,

Firstly, resolved paths were not cached, so I added a fix for that (1ea7c1e). Although the performance win for this one is quite minuscule.

Secondly -- derequire. Now THAT's a serious bottleneck. I suggest to make it optional, which is what 37d434c implements. In my case the bundle performance went from 13-ish seconds to 2 seconds with derequire disabled. And I never had any issues in our huge code-base with derequire off.

Cheers,
M.