fix mirrored scrolling in markdown editor

issue #2426
- ember markdown component now looks for preview element as a DOM ancestor rather than a descendent
Implement signup in Ember

Closes #2410

- Add signup action that posts to signup endpoint
- Fix nav bar showing on signup page
- Fix image link when a user hasn't set their image yet
- Redirect to the ember/signin page if requesting an ember page
Fix content preview actions and add tests

Closes #2798
-fetch full model for active post in Backbone content preview view
-remove unnecessary type check in Models.Post.saving
-add functional tests for all post settings menu actions in editor screen
-add functional tests for all post actions in content preview
 screen for posts with and without tags
correct settings.edit call signature for installedApps

closes #2773

- this is left over from my refactoring work
Merge pull request #2801 from ErisDS/issue-2773

correct settings.edit call signature for installedApps
Merge pull request #2780 from jgable/ember-signup

Implement signup in Ember
Merge pull request #2795 from appleYaks/fix-editor-scroll

fix mirrored scrolling in markdown editor
Merge pull request #2799 from jaswilli/issue-2798

Fix content preview actions and add tests
Ember editor save and publish button functionality

Closes #2747
- Added new 'editor-save-button' view and template.
- Added save action to post controller.
- Set a new post as the default model for the /editor/ route.
- Set the `posts/post` controller as the controller for the /editor/
  route.
- Needs ghost-popover #2418 component for full pop-up functionality
Add active class to settings tabs

Closes #2751
Fix default user cover on settings pane

Closes #2806
- Ensures that the user's cover property is a string, otherwise uses the
  default cover.
Update ember post fixture data.

closes #2803
- corrected status published string
- corrected page to not use invalid choices
- updated id integer to start at 1 and not 0
- updated to repeat 31, added a note about removing post id:0
Merge pull request #2810 from shindakun/fixtureupdate

Update ember post fixture data.
Merge pull request #2804 from novaugust/ember-settings-currently-active-pane

Add active class to settings tabs
Merge pull request #2786 from novaugust/ember-editor-save-and-publish

Ember editor save and publish button functionality
Merge pull request #2807 from novaugust/ember-user-cover-default

Fix default user cover on ember settings pane
Refactore slug API for generating tag and post slugs.

Closes #2601
- Removed slug generation from the post API
- Added new, self-contained slug API
- Fixed slug permissions in the fixtures files
- Added a HTTP route for the new API method
- Added integrational tests
Fix up url helper unit tests

Closes #2817
-use async semantics for tests
-fix api.settings.read stub for the url helper describe block
-rename test to describe actual behavior (return '/' instead of '')
Fix 403 errors after signup

Closes #2819

- Keep around the _csrfSecret on the session after regenerating
Merge pull request #2818 from jaswilli/issue-2817

Fix up url helper unit tests