BLD: add setup_requires in setup.py so numpy can be used with buildout

Numpy is a setup-time dependency due to some .h files, but is not declared as such. This causes tools like buildout to fail.
Merge pull request #3764 from jtratner/fix_division_with_numexpr

BUG: Fix __truediv__ numexpr error
ENH: enable support for iterator with read_hdf in HDFStore (GH3937)

DOC: update v0.11.1.rst
Merge pull request #3803 from jtratner/makefile-updates

BLD: Add useful shortcuts to Makefile
Merge pull request #3949 from jreback/hdf_iterator

ENH: enable support for iterator with read_hdf in HDFStore (GH3937)
Merge pull request #3903 from ejnens/master

BLD: add setup_requires in setup.py so numpy can be used with buildout
TST: Change network decorator to auto-check for network errors

TST: Enforce more strict rules about ignoring IOErrors with network tests
TST: Remove explicit connectivity checks in test cases.

Instead, network decorator in pandas.util.testing checks
for that instead. You have to opt into failing on tests
by setting `pandas.util.testing._FORCE_NETWORK_ERROR` to `True`.

CLN: Move imports and test skip to top of file
ENH: Allow keyword arguments to network decorator

ENH: skip try/except checks if raise_on_error
ENH: Add test decorator 'with_connectivity_check'.

Allows tests to check that a url is available before bubbling up
an error from a test case.
TST: Change tests to use with_connectivity_check to better approximate previous behavior
DOC: Update RELEASE.rst with info on new/changed decorators
TST: Add check_before_test option to with_connectivity_check.