CLN: Make GroupBy inherit from PandasObject
CLN: Make PyTables unicode safe + add StringMixin
CLN: Make StataMissingValue use StringMixin
ENH: Use StringMixin for addl string methods in stats
CLN/ENH: Make Sparse* into PandasObjects

Plus get all the string methods working...
CLN: Index now a PandasObject + str method cleanup
CLN: Make tseries/index fit with PandasObject.
CLN: Cleanup extraneous str methods from Panel
CLN: Change name of TestPandasObjects --> TestPandasContainer
DOC: New class hierarchy + StringMixin
DOC/CLN: Remove extra whitespace from v0.12.0.txt