removing white space at end of blank lines

This PR adds a check for 100% blank lines and makes sure the comment that is added to that line does not include a character of blank white space.

It also centralizes this token creation.

Previously, if there was a file like this...

```javascript
/* feature some-feature:file */
import Ember from 'ember';

var ContentView = Ember.View.extend({
  templateName: 'content'
});

export default ContentView;

```

Then the 3 blank lines (including the one at the bottom) would have a comment with an extra space at the end.  This is causing our javascript style checkers to explode on defeatured code.