Stats: remove empty weeks on post details

[timmyc]

Currently on the Post Details page, the API will return a large amount of data for the past 6 weeks of post views. If the post has recently been published, this results in a bunch of zeros being shown:

When iterating over this logic ( maybe in the parser? ) we should omit week data that happened prior to the post being published. Perhaps we could highlight the date the post was published too?

[timmyc]

Closing in favor of #196