Bug 853341 - Add Timothy Guan-tin Chien and Jordan Santell as contributors in credits.md

 - Added contributors
 - Removed unnecessary comments for ending blocks of name, now that they are grouped by letters
Remove added frame on unload.
Remove traits from the panel implementation.
Merge pull request #928 from Gozala/bug/private-panels@816257

Bug 816257 - Detraitify panel implementation. r=@ochameau
Merge pull request #929 from Gozala/hotfix/unload-frame

Bug 859860 - Remove added frame on unload. r=@ochameau
Bug 837494 - re-implement `contentStyle*` using the new nsIDOMWindowUtils methods

- added `mod` module, with `attach`, `detach`, `attachTo`, `detachFrom` and `getWindowTarget`
- added `loadSheet` and `removeSheet` to `stylesheet/utils`
- added `Style` object in `stylesheet/style`
- replace usage of stylesheet services with `attach`/`detach` a `Style` object
- added `weak-set` module
Merge pull request #839 from ZER0/contentStyle/837494

fix Bug 837494 - re-implement `contentStyle*` using the new nsIDOMWindowUtils methods r=@gozala
Merge pull request #883 from ZER0/credits/853341

Bug 853341 - Add Timothy Guan-tin Chien and Jordan Santell as contributors in credits.md