Adding word count diffs as a property for 'Editor Closed'.

Added word_count word_diff_count properties to the 'Editor Closed'
property to see what a typical length post looks like.
Updated stats call to make it more clear.
Merge pull request #1266 from wordpress-mobile/issues/830-word-count-stats-for-posting

Adding word count diffs as a property for 'Editor Closed'.