no issue
* fix title input padding and placeholder weight
* 🔥 remove unused showdown-ghost dependency
* implement full screen mode via CSS rather than autonav toggle
* implement custom split pane editor preview
- replace SimpleMDE's split pane handling with our own so that we have more control over the element positioning, toggling of our custom fullscreen code, and so that the preview pane can be scrolled separately as per our old editor
* use forked version of simplemde that has the latest CodeMirror compiled
- SimpleMDE hasn't been updated for 11 months and the version of CodeMirror is baked into the SimpleMDE code, to get an up to date version I've forked and re-compiled
- pull in the unminified SimpleMDE source so that it's easier to debug in development, our asset compilation steps will take care of minifying it for production
* fix gh-markdown-editor teardown
no issue
* move "save on first change" behaviour into editor controller
* allow TAB events to be specified in keyEvents hash of gh-input
* replace mobiledoc-kit/gh-koenig with a SimpleMDE based editor
- remove `gh-koenig` in-repo-addon from `package.json` so that test files etc aren't loaded
- remove `mobiledoc-kit` dependencies
- extends `gh-editor` to handle file drag/drop
- adds `gh-uploader` and `gh-progress-bar` components to handle file uploads in a more composable manner
- adds `gh-simplemde` component that wraps SimpleMDE
