Add Rust support.

[meqif]

Hi!

This pull request adds support for Rust files and would close #35.

I apologise in advance for some of the hairier regular expressions. If someone could suggest more efficient or cleaner alternatives, I would be grateful. If not, that's also okay.

[coveralls]

Coverage remained the same at 100.0% when pulling f90ed11 on meqif:rust-support into 7e25680 on jacktasia:master.

[coveralls]

Coverage remained the same at 100.0% when pulling f90ed11 on meqif:rust-support into 7e25680 on jacktasia:master.

[jacktasia]

Awesome! Thanks for doing this. This looks good to me. Just give me a bit to try it out for real and then I'll merge it. Thanks again!

[meqif]

Thank you. 😄
I noticed a small mistake (a "test" instead of "JJJ" in a regular expression). I'll fix that in a jiffy and push a new squashed commit.

[coveralls]

Coverage remained the same at 100.0% when pulling 87d5194 on meqif:rust-support into 7e25680 on jacktasia:master.

[meqif]

I see no more obvious mistakes and the commit was pushed, feel free to merge.

[meqif]

Awesome, thanks for merging!

[jacktasia]

Of course! Thanks again for adding Rust support. FWIW your changes should be available via MELPA in 3-12 hours.