Move JSObfu to a gem and pull it into the Rex namespace.

Moves JSObfu out to its own repo/gem, with a bunch of new specs/fixes/features. External interface remains the same.

##### Verification

- [x] ie_setmousecapture_uaf - pass
- [x] ie_cgenericelement_uaf - pass
- [x] ie_cubtton_uaf - pass
- [x] ms13_069_caret - pass
- [x] ms13_055_canchor - pass
- [x] ms14_012_textrange – pass