CLN/INT: rename *possibly* -> *maybe* functions

[jreback]

we have a mixed bag on naming this. Let's change possibly -> maybe. Keep everything else the same. (if you do the same search for maybe you will fine it to be far more common). Note that the usage of these functions will have to be renamed as well :>

(pandas) bash-3.2$ grep --include '*.py'  -R possibly pandas |grep def
pandas/computation/expr.py:    def _possibly_transform_eq_ne(self, node, left=None, right=None):
pandas/computation/expr.py:    def _possibly_downcast_constants(self, left, right):
pandas/computation/expr.py:    def _possibly_eval(self, binop, eval_in_python):
pandas/computation/expr.py:    def _possibly_evaluate_binop(self, op, op_class, lhs, rhs,
pandas/core/internals.py:def _possibly_compare(a, b, op):
pandas/indexes/base.py:    def _possibly_promote(self, other):
pandas/tests/types/test_cast.py:    def test_possibly_convert_objects_copy(self):
pandas/tseries/index.py:    def _possibly_promote(self, other):
pandas/tseries/tdi.py:    def _possibly_promote(self, other):
pandas/types/cast.py:def _possibly_convert_platform(values):
pandas/types/cast.py:def _possibly_downcast_to_dtype(result, dtype):
pandas/types/cast.py:def _possibly_cast_item(obj, item, dtype):
pandas/types/cast.py:def _possibly_convert_objects(values, convert_dates=True, convert_numeric=True,
pandas/types/cast.py:def _possibly_castable(arr):
pandas/types/cast.py:def _possibly_infer_to_datetimelike(value, convert_dates=False):
pandas/types/cast.py:def _possibly_cast_to_datetime(value, dtype, errors='raise'):

[jreback]

cc @gfyoung

[gfyoung]

Seem reasonable.

[jreback]

also (separately), we should rename all of the functions in pandas.types.cast to remove the leading _. Just for some readability (they were like this because they were explicity private when I ported from pandas.core.common). pandas.types is private so this is not big deal now.

[StanczakDominik]

Figured I would take a stab at this one.