Starting migration
oops
Can work with from_storage of old and new
add verbose migration messages
add eq / neq methods for fields; reload fields on attr access
make validators comparable
examples for migration
update examples
Merge branch 'feature/migration' of https://github.com/CenterForOpenScience/modular-odm into feature/migration

Conflicts:
	modularodm/StoredObject.py
	modularodm/storage/__init__.py
misc bug fixes, optimizations, and documentation:

only delete back-references on foreign fields that specify a backref key
deleted extra calls to to_storage in save and _get_list_of_differences_from_cache
simplified FlaskCache
added docstrings
add lazy_default variable to Field: set to False to disable lazy imputation of default values
initial commit of abstract foreign fields
clean up comments
set lazy default to false on auto_now, auto_now_add
add elemMatch selector
don't require objects to be loaded
update examples
Merge branch 'feature/abstract' into develop
fix reversed
fix slicing; must override __getslice__ method