Promise chains can now be expanded / collapsed.

- Chains containing all fulfilled promises are collapsed by default.
- Chains containing at least one rejected promise are expanded by
  default.
- Chains containing a pending promise are expanded until the first
  pending promise.
Fix test after collapsing fulfilled promises by default
Replace  button with Stack trace for promise errors
Stop cleaning dist_chrome on every build

Commit 497c568cef77db519a3b1d423a44003a23ac267b started to clean
dist_chrome before every build so we can detect missing vendor files
instead of them staying permanently on a developer's machine, while
failing on new clones.

The problem is that it is not possible to block the extension refresh
during build, which is causing very annoying errors.

I kept cleaning firefox_dist so we can at least detect missing files
when testing Firefox.
Eagerly inject ember_debug when Reload button is clicked.

Page navigation detection by Chrome API is inaccurate and late.
Instead we have to inject ember_debug eagerly when the Reload button is
clicked in the promise tab.
Bump version to 1.2.0
Update README.md
Update README.md
Replace dummy urls _unused_dummy_... with empty strings
FIX: changes needed to fix permission denied exception on Firefox >= 30

 - https://github.com/emberjs/ember-inspector/issues/147
 - https://blog.mozilla.org/addons/2014/04/10/changes-to-unsafewindow-for-the-add-on-sdk/
Merge pull request #149 from rpl/fix/permission-denied-exception-on-firefox-30

FIX: changes needed to fix permission denied exception on Firefox >= 30
Stringified json should not get extra quotes when edited in the object inspector

Fixes #150
Use SVG badge in README
Merge pull request #151 from seanlinsley/patch-1

Use SVG badge in README
FEATURE: New "Render Performance" menu item to profile rendering speeds
and help diagnose issues.
Send added node profiles instead of the entire render tree
Update render to tree to look and feel like the other tabs

- Updated render tree UI
- Added render tree tests
- Upgraded Ember
- Fixed failing promise tests from ember upgrade
Update render performance nav icon
Update render list empty notice to look like the other tabs
Remove file added by mistake render_tree_test.js