Revert "Update Ultisnip mappings"

This reverts commit 07d573aa310a06d6745f85f2d1176f8782fea630.
Revert "Switch to UtliSnips from vim-snipmate"

This reverts commit 219994876fde963a50a66c7ad4bc92f3c5e8982e.
Add a couple of Slate settings...

Still very much learning the ropes with this app.