BUG: Conflict between thousands sep and date parser.

Fixes issue where thousands separator could conflict with date
parsing.

This is only fixed in the C parser.

Closes issue #4678
BUG: fix issue #4678 for Python parser
Fixes wrong overlapping check in _can_fast_union.

To use the fast_union method it is not enough to find an overlap, the
indices also have to be aligned.
BUG: Fix appending when dtypes are not the same (error showing mixing float/np.datetime64) (GH4993)
BUG: Fix for DateOffset's reprs. (GH4638)
BUG: wrong index name during read_csv if using usecols

Closes #4201

If user passes usecols and not names, then ensure that the
inferred names refer to the used columns, not the document's
columns.
BLD: numexpr 2.2.2 fixes incompatiblity in PyTables 2.4 (GH4908)

DOC: removes incompat warning
BUG: allow Timestamp comparisons on the left

Now tested with Series and DataFrame
BUG: Fix Timestamp compares to NaT

For example

    Timestamp('now') > pd.NaT

should return the same result as

    pd.NaT < Timestamp('now')

but before this commit it didn't because when Timestamp was on the left, the
values were compared whereas if NaT is on the left then the truth values are
hard-coded based on rules like NaN.
PERF: add vbench for DatetimeIndex unions/intersetions
PERF: add Timestamp <-> Series comparison vbench
CLN: move resolvers getter to generic.py
PERF: add vbench for datetime comparisons
ER: give concat a better error message for incompatible types
DOC: prior version section in v0.13.0
BUG: Fix a bug when indexing np.nan via loc/iloc (GH5016)