Added folding for project find results

Allows users to fold results in the project fine result view, hiding all results for a single file.  The folding can be done either by clicking on the file in the results list or pressing the left and right arrow keys.

![out](https://cloud.githubusercontent.com/assets/4984331/3633937/13988a14-0f07-11e4-9fb3-78670297c7b4.gif)

resolves #98

This is confusing. Maybe keep the old text, split them into describes

```
describe "when there are collapsed results", ->
  it "moves to the correct next result when a path is selected", ->
  it "moves to the correct previous result when a path is selected", ->
describe "when there are no collapsed results", ->
  it "moves to the correct next result when a path is selected", ->
  it "moves to the correct previous result when a path is selected", ->
```