Add EditorConfig to make code style formatting easier

[dtognazzini]

EditorConfig helps developers define and maintain consistent coding styles between different editors and IDEs. The EditorConfig project consists of a file format for defining coding styles and a collection of text editor plugins that enable editors to read the file format and adhere to defined styles. EditorConfig files are easily readable and they work nicely with version control systems.

http://editorconfig.org/

Rubymine and other commonly used editors support this.

[alecjacobs5401]

I added an editor config to the web repository. I can copy it over here, but I'm not sure how we can utilize a shared one.