Update slug API to work with additional types

Closes #2866
-update slug API to handle users and apps in addition to
 posts and tags
-update existing tests
-add new functional tests for slug endpoint on http api
Enable post deletion from Ember admin

Closes #2849
-wire up delete post action in ember admin
-refactor ember modal dialog
-override RESTAdapter.deleteRecord to workaround Ember expecting
 an empty response body on DELETEs
Merge pull request #2873 from jaswilli/2849-delete-posts

delete posts from post settings menu
Cache invalidation for post update

closes #2833
- Handle status change of post
Fix error when running Ghost with a socket

fixes #2879
- Syncronously unlink old socket file
Merge pull request #2877 from jaswilli/2866-slugs

Update slug API to work with additional types
Merge pull request #2876 from halfdan/2833-rasperize-cache

Cache invalidation for post update
Merge pull request #2880 from halfdan/2879-socket-issue

Fix error when running Ghost with a socket
Fix Editor/:postId 404 on draft

closes #2857
- in EditorRoute, get model from the datastore if it's there
- if page is refreshed, get model from `/posts` API with `{status: 'all'}`
Close post settings popover menu after delete post

No issue
-inject popover:service into modal component delete post
 controller so popover close can be triggered as part of
 the delete action
-remove unnecessary 'needs' from the delete post controller
Merge pull request #2894 from jaswilli/close-popover

Close post settings popover menu after delete post
Merge pull request #2892 from appleYaks/draft-404

Fix Editor/:postId 404 on draft
Implement the Tag Editor view

closes #2425

- creates custom view for the tag editor
Clear any existing SIGINT listeners during startup

No issue
-remove any existing listeners on the SIGINT event during
 the ghost bootstrap process.  handles an issue during testing
 where node was warning about too many listeners.
Merge pull request #2903 from jaswilli/bootstrap-listener

Clear any existing SIGINT listeners during startup
Fix HTML preview rendering on the main screen

closes #2904
- The `posts/post` template now takes its HTML from the post model instead of using the editor's markdown component
Merge pull request #2901 from hswolff/tag-editor

Implement the Tag Editor view
Implement a Generic Uploader - #2886
Merge pull request #2905 from appleYaks/preview-markdown

Fix HTML preview rendering on the main screen
Removed API dependency from mailer and api/mail

Fixes #2836.

* Mailer now only handles sending email and initializing settings. Instead of adding new notifications there, it just sets flags on its own object.
* Mailer now checks for the presence of "to". If there is none, it fails. You should really pass a full mail object complete with "to", "subject" and "html", otherwise it's partial content.
* Therefore Mail API doesn't check for the existence of the "to", and doesn't get the email from settings and substitute that
* index.js now has a method that adds the notifications. I figured adding those THERE is probably better than individually in every module. It is, as the comments say, can be made extensible