Dont remove mixins

Starting in [`jade@1.2.0`](https://github.com/visionmedia/jade/blob/master/History.md#120--2014-02-26) mixins weren't added to a compiled template unless they were called from within that template. This is a good feature that cuts down on file size.

The only problem with this is that the [mixin support](https://github.com/HenrikJoreteg/templatizer#mixin-support) added by templatizer allows mixins to be namespaced on the file that they were declared in, so they could be called separately (like `templatizer.fileName.mixinName()`).

This PR adds an option `dontRemoveMixins` that is `false` by default to allow that feature in jade to be turned off when compiling.

Other changes:
- Update `jade`
- Update `testee`
- Update `precommit-hook`