Add Core Data stack

Add a basic Core Data stack
Add Market entity

Add a Market entity to Core Data stack.  Use Mantle to convert MTLModel object into Core Data entity.

Add value tranformer for converting NSArray to NSData.
Implement managed object subclass

Refactor class names in advance for implementing managed object subclass.

Implement subclass and category for custom accessors.
Continue to build out Core Data infrastructure

Save more market fields into managed object.  Add transformer for CLLocation.
Reimplement indexed table view

Use the fetched results controller for building index on table view.
Add predicate builder
Start moving fetched results controller around

Move FRC to data manager.  Begin to add a second FRC for searching
Begin to reimplement search
Don't search on nil strings
Merge branch 'core-data'