Rebuild Post Settings Menu

Closes #2845. 

- Renamed `gh-blur-text-field` to `gh-blur-input`
- Changed title input in `editor.hbs` to use a `gh-blur-input`
- Added `regenerateSlugPlaceholderFlag` property `Post` model
- Blurring the post's title toggles the `regenerateSlugPlaceholderFlag`, removing api
  spam on title change (previously, regenerated on every change in title)
- Created `SlugGenerator` class to generify slug generation.
- Added `timestampVerification` function to `utils/date-formatting`
- `utils/date-formatting` now uses `strict` parsing of dates
- Added more acceptable date formats to accommodate strict parsing
With the change to use the `slugGenerator` I think that we should bind to `slugGenerator.slug` (or whatever the prop is), and instead of toggling `regenerateSlugPlaceholderFlag` in the action, just call `this.get('model.slugGenerator').generate(this.get('title'))`.