LANGUAGE: Add language `R`

I just discovered Bountysource and was interested in projects/bounties related to the [R](http://www.r-project.org/) language (`language:R`). However, https://www.bountysource.com/bounties/search does not seem to recognize `R` as a language. (There are certainly bounties on issues related to R).

Are languages automatically pulled from GitHub or do they have to be manually added/requested? If the latter, please add R.
##

Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/7098071-adding-language-r?utm_campaign=plugin&utm_content=tracker%2F47&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F47&utm_medium=issues&utm_source=github).