added halflife to exponentially weighted moving functions
TST: added null conversions for TimeDeltaBlock in core/internals related (GH4396)
CLN: Refactor arithmetic operations to core/ops

* Abstract all arithmetic methods into core/ops
* Normalize arithmetic methods signature (see
  `ops.add_special_arithmetic_methods` and `ops.add_flex_arithmetic_methods`
  for signature).
* Opt-in more arithmetic operations with numexpr (except for
  SparsePanel, which has to opt-out because it doesn't respond to
  `shape`).
* BUG: Fix ``_fill_zeros`` call to work even if TypeError (previously
  was inconsistent).
* Add bind method to core/common
* Add full range of flex arithmetic methods to all NDFrame/ndarray
  PandasObjects (except for SparsePanel pow and mod, which only work for
  scalars)
* Add a set of testing methods to check that numexpr was actually used
  successfully.
* Flesh out test cases to include all arithmetic ops + test refactoring
* Disable numexpr for sparse objects (they don't work correctly right
* now)
* Sparse methods aren't moved because they are very specific to sparse
  (and aren't numexpr accelerated)
* Disable r* comparisons for now because they cause test failures
* Specifically allow radd in TimeOps for Series
* Fixup Series time rops and add a few test cases.
* Disable flex r-ops for bools (no good test cases yet...)
* TST: Remove tests for TypeErrors in pandas/computation/test_eval that
  now work after this refactor (because DataFrame now defines more r*
  methods)
BUG: Fix DateOffsets to return NotImplemented when types do not match

Enable test cases that involve these DateOffsets with `__r*` ops
Merge pull request #5022 from jtratner/arithmetic-refactor2

CLN/ENH: Provide full suite of arithmetic (and flex) methods to all NDFrame objects.
Merge pull request #5040 from jreback/sparc_fix

TST: added null conversions for TimeDeltaBlock in core/internals related (GH4396)
COMPAT: provide numpy compat with 1.7 for numeric methods when calling like: np.prod(obj)
        as numpy is now passing extra args to the pandas methods!
CLN: refactor all numeric type stats methods to core/generic.py
     from the object level modules (e.g. mean/sum/min/max....)
CLN: refactor cum methods to core/generic.py
CLN: make_stat_function for numeric methods in core/generic.py
Merge pull request #4998 from mortada/halflife

added halflife to exponentially weighted moving functions
BUG: Warn when dtypes differ in between chunks in csv parser

closes #3866

Silently fix problem rather than warning if we can coerce
to numerical type.
Merge pull request #5034 from jreback/numpy_compat

BUG/CLN: numpy compat with pandas numeric functions and cln of same (GH4435)
Merge branch 'issue-3866-column-conversion' of https://github.com/guyrt/pandas into guyrt-issue-3866-column-conversion

Conflicts:
	doc/source/release.rst
	pandas/io/tests/test_parsers.py