added (l/r)angle to ultisnips,added mathfonts to snippets

[kevinywlui]

Added some snippets that I've been using often.

(First time using git in a nontrivial manner, hope I'm doing this right.)

[lpil]

Hello! Thanks for your contribution :)

What made you decide to add those ones to the ultisnips format, and those ones to the snipmate format?

[kevinywlui]

I looked through both the ultisnips formatted file and snipmate formatted file and placed these snippets near similar ones.

To be honest, it's still unclear to me when to use each format. I've read through #363. But I'm not sure what the final decision is. It seems like most of the .tex snippets can be implemented in the snipmate format.

[lpil]

Best to stick everything in the snipmate format in my opinion :)

[kevinywlui]

Updated. Also fixed a conflict with 'eq' snippet between snipmate and ultisnips.

[lpil]

Great. Could you indent with tabs rather than spaces please? :)

[kevinywlui]

Fixed!

[lpil]

Thanks! :D

[kevinywlui]

Thanks for all the help! I really appreciate it!

[lpil]

Not at all, thank you for contributing