BUG: Fix to_datetime to properly deal with tz offsets #3944

Currently for certain formats of datetime strings, the tz offset will
just be ignored.
DOC: Clarify that DataFrame string formatters must return strings

I am not 100% sure that string formatters must really return *unicode* strings
(non-unicode strings seem to work, too), but I am leaving that because it's
what is already documentated.

Fixes #6052.
BUG: fix broken BigqueryError reference
Replace network decorator with with_connectivity_check

Network decorator was ignoring test failures due to API changes in
external services.
ENH: allow legend='reverse' in df.plot() GH6014
Merge pull request #6111 from jtratner/swap-network-decorator

Replace network decorator with with_connectivity_check
BLD: travis reports job names to ScatterCI
BLD: travis reports job names to ScatterCI
Add Scatter-CI link to README.md
PERF: fix JSON performance regression from 0.12 (GH5765)
Merge pull request #6080 from dsm054/fix-gbq-bigqueryerror

BUG: fix broken BigqueryError reference
Merge pull request #6137 from Komnomnomnom/json-0.13-slowdown

PERF: fix JSON performance regression from 0.12 (GH5765)
DOC: v0.13.1.txt updates
BLD: use newer versions of numexpr with numpy 1.8
Merge pull request #6141 from jreback/numexpr

BLD: use newer versions of numexpr with numpy 1.8
BUG: Bug in DataFrame construction with recarray and non-ns datetime dtype (GH6140)
Merge pull request #6142 from jreback/from_records

BUG: Bug in DataFrame construction with recarray and non-ns datetime dtype (GH6140)
ENH: Add unique and nunique to GroupBy whitelist

Series.unique and Series.nunique are useful methods for querying the
unique elements (or number of unique elements) in each group when used
in conjunction with DataFrame.GroupBy.  This commit addresses
pydata/pandas#6146.
ENH: Updated tests for series GroupBy whitelist

Added tests for fix to pydata/pandas#6146.
Merge pull request #6147 from bburan-galenea/bburan/groupby-series-unique

ENH: Add unique and nunique to GroupBy whitelist