First shot in removing cache magics (cf #54)
Merge remote-tracking branch 'origin/hashfield' into RIP_cache

Conflicts:
	limpyd/fields.py
	limpyd/model.py
	tests/model.py
Merge remote-tracking branch 'origin/master' into RIP_cache
Merge pull request #74 from yohanboniface/RIP_cache

RIP cache