ENH: Add `isin` method to DataFrame.

docs. to be rebased

ENH: Add isin method to DataFrame

Basic tests.

Added method and fixed tests.

ENH: Add ordered argument to df.isin()

Expects a sequence of arrays.

Updated release notes for df.isin()

CLN: cleanup

going to remove ordered argument.

Using a dict for ordered matching. Docs

BUG: fixed subselection length check issues.

Updated release notes for df.isin()

remove merge conflict note
ENH tweak DataFrame isin method
ENH add iloc argument to DataFrame isin
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
Merge pull request #4296 from neurodebian/master

Use psutil to set process affinity (test_perf.py) + minor pylint-friendliness for ._ix
DOC: docs for precise_float option in read_json
Merge branch 'Komnomnomnom-ujson-precise-float'
Merge pull request #4302 from jreback/nat_convert

BUG: explicity change nan -> NaT when assigning to datelike dtypes
Merge pull request #4299 from Komnomnomnom/ujson-small-floats

ENH: ujson better handling of very large and very small numbers, throw ValueError for bad double_precision arg #4042
TST: change a small float comparison to np.allclose
DOC: cookbook addition
Merge pull request #4307 from jreback/ujson_small_fix

TST: change a small float comparison to np.allclose (GH4306)
CLN: remove try suite in _read

A skip will now occur if a call to urlopen or a read from the resulting object
throws a urllib2.URLError exception
DOC: add 0.13 to release notes
TST: make sure test passes even if componnents link isn't present
Merge pull request #4310 from cpcloud/network-failure-hack

TST: make sure test passes even if components link isn't present
DOC: cookbook example
TST: skip some tests if scikits is installed but not scipy GH3376