FIX: change initObjToJSON return type

This is necessary because clang complains about the return type. There's a call
to the macro import_array() which injects a return statement into wherever it's
used.
DOC: minor io.rst edits
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.
TST: json tests to int64 to avoid dtype issues
TST: skip tests if xlrd has lower than needed version
TST: skip pickle tests on not-little endianess
TST: skip test_encoding on non-little endian in test_pytables
TST: skip some stata tests on non-little endian
TST: convered skips on knownfailures to knownfailures (test_pickle/test_stata)
Merge pull request #3898 from jreback/test_fixes

TST: test fixes for various builds (debian)
TST: convert knowntestfailures to skip tests
Merge pull request #3906 from jreback/test_fix2

TST: convert knowntestfailures to skip tests
BUG: fix unicode -> str cast in tslib

This should use format since calling str on a unicode string is a *bad* idea
because it may or may not repr correctly.
Merge pull request #3900 from cpcloud/tslib-fix

BUG: fix unicode -> str cast in tslib
CLN depreciate save&load in favour of to_pickle&read_pickle

DOC replace save&load with to_pickle&read_pickle
FIX not mention save/load being removed
Merge pull request #3787 from hayd/read_pickle_and_to_pickle

CLN deprecate save&load in favour of to_pickle&read_pickle
BUG/CLN: remove infer_types
BUG: fix bug with replace when a compiled regex was passed but regex=False
TST: add tests for new com functions