TST: ujson dont force endianness #4274
Update CONTRIBUTING.md with note on attribution in PRs
DOC: Fix typo.
TST: print out byteorder in ci/print_versions.py
ENH: test_perf.py - use psutil to set affinity (if absent functionality - then affinity module)

original affinity module is not commonly installed, has known issues,
and was not updated since 2006.  psutil is already used in parts of
pandas, so it would be logical to use it instead by default.
minor: some trailing spaces and a pylint "pragma" to stop complaining about Series._ix defined elsewhere
ENH: ujson better handling of very large and very small numbers, throw ValueError for bad double_precision arg #4042
ENH: expose ujson precise_float argument on decode
BUG: explicity change nan -> NaT when assigning to datelike dtypes
DOC: docs for precise_float option in read_json
TST: change a small float comparison to np.allclose
DOC: cookbook addition
DOC: add 0.13 to release notes
TST: make sure test passes even if componnents link isn't present
ENH: Add date_format keyword to to_csv()