DOC: prepend missing >>> to docstring Examples in set_index.
BUG: handle single column frame in DataFrame.cov
Merge pull request #2992 from jreback/docs

DOC: doc updates/formatting in basics,indexing,10min
Merge pull request #2975 from dieterv77/FixCovIssue

BUG: handle single column frame in DataFrame.cov
Merge pull request #2851 from meteore/fix-set_index-docstring

DOC: prepend missing >>> to docstring Examples in set_index.
ENH: numexpr on boolean frames

BLD: add highly recommended depdencies section and setup.py changes to optionally build these

ENH: add binary_ops vbench
     add binary_ops accelerations via ne
     created expressions.py core module

ENH: added support for remainder of comp and compare methods
     added vbench for add/mult

BUG: catching error in boolean comparisons if type is int and trying to put NA
     fixed failing tests from boolean comparisons
     removed radd operations from numexpr
     numexpr to now ignore a failing type operation and fail over

TST: failing test because float16 not upcasted on 32-bit....weird

TST: added test_expressions test suite
     added ability to turn off usage of numexpr (mainly for testing)
     restricted ops to allowed dtypes and min shape of input
ENH: added ability to use single or multi-threads in numexp testing

TST: updating test_expressions to test with 1 and num_cores

ENH: added module level function in core/expressions to change use of numexpr

BUG: using set_use_numexpr now changes the evaluation functionsx