Add icons for R, Julia and Stata

[vikjam]

I'm really digging this theme, and since I mostly use Sublime with statistical languages, I noticed the icons for R, Julia and Stata were missing. I think the scopes for these file extensions are as follows:

source.r, source.r-console
source.julia
source.stata

And the following icons:

I could put together a pull request if that's easier.

[kevin-snippet]

will be cool to have icons for R and Stata! work with them everyday :)

[jackolney]

+1 on this. R icons would really perfect this theme for me!

[vikjam]

In a fork, I added the icons. Take a look by just cloning the fork to your packages:

• Go to the directory containing your packages (which you can see by going to "Browse Packages.")
• Then run, git clone https://github.com/vikjam/afterglow-theme

Here's a screenshot of the Julia, R and Stata icons among the other ones supported by this theme:

If you notice any problems or have any thoughts on how to improve, feel free to make changes to the fork. When we figure it out, I'll make a pull request to the main project here.

[jackolney]

Thanks for the updates @vikjam looks great! Just needs a pull request into the main project now. Definitely the most useful theme in ST.