kaiso test refactor
Fixtures to go with that refactor...
Removed "if not translations" messiness
NotNullValue -> constants.PlaceholderValue
Empty string support + new tests
Merge branch 'master' into translate-empty-string-kaiso

Conflicts:
	taal/kaiso/__init__.py
	taal/sqlalchemy/types.py
Addressing code review
Clearer attribute names
Better test
Converting placeholder string to placeholder class on deserialize from database
Better comment
revert back to only treating nulls as transparent
merge master
Merge pull request #18 from onefinestay/translate-null-only

Translate null only