Bump grunt-contrib-uglify and pin versions of grunt packages

[astorije]

Made different tests locally and it seems to work fine (only change is grunt-contrib-uglify) but since this can break publication, I wouldn't be against some more testing from other reviewers :-) (will not set the second review needed label myself for this reason).

[xPaw]

👍 Since we had ~ and ^ versions already, we unintentionally tested newer version :)

[astorije]

Actually, not quite: all of them but grunt-contrib-uglify still have their stable version matching the versions we have in the package.json.
Only grunt-contrib-uglify changes, as prior to that PR, we were matching 0.5.0 and 0.5.1, while this PR makes it go to 0.11.1. Other are just pinned with no other consequences.

[maxpoulin64]

Looks fine to me, 👍 I'm not a fan of pinning versions, but as discussed with @astorije on IRC on the long term it's the safer approach. Lets just not forget to keep them updated once in a while not to fall too far behind :)

[AlMcKinlay]

Might be worth using libraries.io to make sure we don't fall behind. Emails maintainers when something is updated.

[astorije]

We actually do have a libraries.io page as I contacted them when starting to fix that page which was not working properly...
However, we also use badges from https://david-dm.org/thelounge/lounge, which also works pretty well. Just need to keep an eye on dependencies :-)