Changed ember models to use moment for dates

Closes #2888

-Added moment-date `DS.Transform`
-`models/post` and `models/user` both use `DS.attr('moment-date')` in
place of `date` now.
Make debug an authenticated route
Handle invalid post ids in editor route

No issue
-fail fast if an invalid post id is passed into the
 editor route to prevent an unnecessary network request
 for all posts
-if post id is valid but post does not exist, transition
 to Content screen instead of returning an invalid model
Update user model logic for Ember Inspector.

Fixes #2921.
Merge pull request #2916 from jaswilli/editor-route

Handle invalid post ids in editor route
Merge pull request #2889 from novaugust/post-model-dates

Changed ember models to use moment for dates
Merge pull request #2917 from jaswilli/debug-cleanup

Make debug an authenticated route
Make exports consitent.

Previously, the exports were somewhat random with some files declaring
local variables then immediately exporting them, and others simply
doing the work needed in the export itself.
Merge pull request #2922 from lholmquist/user_model

Update user model logic for Ember Inspector.
Merge pull request #2915 from rjackson/make-exports-consistent

Make exports more consistent.
Fix export of data during database migration

Closes #2927
-refactor exporter to export tables that exist in the
 database instead of keying off of schema.js
-move some shared database utility functions into their
 own module
Merge pull request #2928 from jaswilli/issue-2927-export

Fix export of data during database migration