Only create a new basket when needed

Previously, a new basket was being created whenever a user visited the homepage, which was causing unneccessary data to be added to the database. The Pages controller has been updated to only load existing baskets and return a null basket if no basket exists.

https://trello.com/c/I9gBjsd3

![](http://www.reactiongifs.com/r/uhwht.gif)
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