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.
BLD: Add useful shortcuts to Makefile

BLD: Add doc task to Makefile
BLD: Make doc not silent

BLD: add tasks to .PHONY

BLD: Only remove *.pyc with make build
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
API: more consistency in the to_datetime return types (give string/array of string inputs) (GH3888)
BUG: truncate will only try to convert to dates for an all_dates index