Add basic rename a variable / refactoring support

[basarat]

No description provided.

[nycdotnet]

On a plane and thinking about future wish list stuff.

• extract interface from class, module, or function
• copy type from variable
• implement stub (to enable "use first" programming flow). doStuff(p1 : string) doesn't exist on MyClass - would you like to implement it?
• "Declare this" refactoring on an instantiated variable.
• Declare all refactoring on a constructor function

[basarat]

Reuse this if you can : https://github.com/atom/find-and-replace/blob/master/lib/find-view.coffee