Add Serialization function

Adding serialization functionality per https://docs.djangoproject.com/en/dev/howto/custom-model-fields/#converting-field-data-for-serialization
Merge pull request #15 from benjaoming/master

Fix South problem
Merge pull request #17 from gcallaghan/master

Issue 9 Deserialization Resolution
Fixed import error in Django 1.5 for LOOKUP_SEP

Fix documented here: https://github.com/toastdriven/django-tastypie/issues/671
Quick cleanup
Merge pull request #20 from hank/master

import for LOOKUP_SEP in Django 1.5
valid django 1.3+ settings
Merge pull request #21 from FPurchess/settings

valid django 1.3+ settings
merge with upstream