Merge pull request #16 from SimpleReviews/prod-reviews

Prod reviews
Merge pull request #17 from SimpleReviews/prod-reviews

more changes
updated denormalize functions

- fixed denormalize functions so that they only update a specific item in a collection, rather than going through every item in a collection. This drastically improves performance!
Merge pull request #18 from SimpleReviews/fix/denormalize

updated denormalize functions
added page header class to product page