add editorconfig file to unify coding style

  [EditorConfig](http://editorconfig.org/) is a means to help developers keep a consistent coding
  style across IDEs/editors. This way we can all  speak and edit in the same way.

  @bluesmoon If theres not everything you require for your work on boomerang please tell me
  and I'll append it. 
so then let's just stick to single tab indents instead of 8 space indent