Move Ultisnips snippets into dedicated vim-snippets repo

[lpil]

Hello!

I'm one of the maintainers of vim-snippets, a project that aims to be a universal source for vim snippets.

I propose that we transfer the snippets from this repository to that one. The main advantage of this is that it means that users of this plugin are not forced to use your snippets.

Additionally, the vim-snippets repo is more actively maintained, and has a larger userbase.

I would also convert the snippets into the snipmate format, as this would allow more vim users to make use of the snippets.

Cheers,
Louis