Resample docstring default values changed

This docstring seems better, since TimeGrouper specifies it [that way][1] too:

[1]: https://github.com/pydata/pandas/blob/master/pandas/tseries/resample.py#L27
Remove confusing default val hints from docstrings
TST: test for GH2623, object in frame upconverting a datetime64[ns] in another column
BUG: GH2817, raise the correct KeyError that the multi-index is not sorted
DOC: add example and warning on fallback indexing for float indexes.
BUG: fix cython caching in setup.py
BUG: fix NameError issue in GH2787
Merge pull request #3135 from jreback/GH2787

BUG: fix NameError issue in GH2787
ENH: added selection to an unordered timeseries the same semantics as an ordered timeseries (GH2437)
Merge pull request #3136 from jreback/GH2437_2

ENH: GH2437 added selection to an unordered timeseries
ENH: GH3070, extend slicing semantics for datelike indexed DataFrames with a string to work like
     TimeSeries (e.g. df['2001'] works)
DOC: cookbook examples
CLN: cleanup arguments in generate_code.py
PERF: Limit memmove to >= 256 bytes, relax contiguity requirements

 (only the stride in the dimension of the copy matters)
Merge pull request #3137 from jreback/GH3070

ENH: GH3070 allow string selection on a DataFrame with a datelike index, to have partial_string semantics (like Series)
Merge pull request #3124 from jreback/GH2817

BUG: GH2817 raise the correct KeyError that the multi-index is not sorted
Merge branch 'stephenwlin-memmove-limit'

* stephenwlin-memmove-limit:
  PERF: Limit memmove to >= 256 bytes, relax contiguity requirements
  CLN: cleanup arguments in generate_code.py
DOC: update RELEASE.rst
BUG: GH2903, implemented xs for axis=1 with a level specified
Merge pull request #3125 from jreback/GH2903

BUG: GH2903 implemented xs for axis=1 with a level specified