Readme talks about file that doesn't exist

[mackstann]

Readme says:

The basic usage of the SetCoLa compiler is shown below. This behavior is demonstrated in the file editor.js.

There is no file called editor.js, nor can I find any file with contents similar to what's shown in the following section.

[jamesscottbrown]

The editor file is in the gh-pages branch: it looks like the main branch contains code for the library itself, and the gh-pages branch contains code for the online editor at https://uwdata.github.io/setcola/.