Added convenient order-by lookup methods
Merge pull request #16 from allenwei/fix-insert-NSDecimalNumber

Fix NSDecimalNumber write precision
fix decode NSDecimalNumber when value is TEXT
Fix crash when tapping on a person's cell after that cell had been scrolled off screen, then scrolled back onto screen.
Fix #20
New instance methods: saveWasRefused, saveDidFail (helpful for debugging — for instance, you may want these to throw exceptions or assert)
Exposed custom field serialization to subclasses.

Removed automatic serialization of NSDecimalNumber since it was problematic to generalize (#19). Models wanting NSDecimalNumber serialization should use the new serializedDatabaseRepresentationOfValue/unserializedRepresentationOfDatabaseValue methods to perform their own serialization according to their needs.
Pulling example bugfix from https://github.com/crossforward/FCModel
Fixed bug where e.g. @"1" and @(1) could be different instances
Experimental support for delayed/batched notifications for better performance when modifying large numbers of items (an app's initial sync, bulk changes, etc.).
Replaced _FCModelMetadata table with PRAGMA user_version (#22).
Some utilities I've found useful
Fixed missing files in test project
Added features requested by #25 and #26.
New cachedInstancesWhere method, using a basic invalidate-on-write query cache.
Removed debug logging
New generic cachedObject system, like cachedInstancesWhere but for arbitrary data with a generator block
Esoteric fix: if you have a DB column name that matches a readonly property, FCModel will now ignore it and log a warning to the console, rather than KVO-crashing when trying to set it.
Improving the class-check system for column serializations of NSURL, NSDate, NSDictionary, NSArray
NSDate overflow for 32-bit NSInteger's