Changes some DataFrames inplace for performance.
Typo in README.rst.
[Verbose display] Improves performance by fetching all cache keys in a single query.
[Verbose display] Simplification using pandas instead of pure python.
Logical simplification.
Replaces math.isnan with simple None comparisons.
Merge branch 'master' of https://github.com/BertrandBordage/django-pandas

Conflicts:
	django_pandas/managers.py