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
Can you make the `slugGenerator` a computed (I think this will simplify some logic below).  Something like:

```javascript
slugGenerator: Ember.computed(function() {
  return SlugGenerator.create({ghostPaths: this.get('ghostPaths')});
}),
```

Then in `slugPlaceholder` you simply know you have a `slugGenerator` since it is created lazily upon calling `this.get('slugProperty')`.