Updates slick lib files

[sbremer]

I needed the frozenColumn feature from (https://github.com/ddomingues/X-SlickGrid) this fork of slick.

Please test before merging, I did some testing, yet my knowledge of proper JS testing is very limited.

After merging this change has to be reverted:

-REMOTE_URL = ("https://cdn.rawgit.com/quantopian/qgrid/"
+REMOTE_URL = ("https://cdn.rawgit.com/sbremer/qgrid/"

[TimShawver]

Thanks for this. I'm going to be making some big changes to the way we load dependencies in qgrid so I think I'm going to merge those changes first before making a change like this. Somebody else wanted to use a different fork (https://github.com/6pac/SlickGrid) so I'm thinking probably what I should do is allow people to specify the name of the npm package they want to use for the slickgrid dependencies. This way people can use whatever fork they want to use.

For context, the branch I'm working on is here https://github.com/quantopian/qgrid/tree/widget-guidelines. It's still a work in progress but basically I'm moving to the suggested "best practices" for packaging/deploying widgets, which means getting slickgrid dependencies from npm. This should allow us to easily switch between the various slickgrid forks that are available on npm.