Merge pull request #2614 from jreback/vbench_fix

BUG: trivial fix in vb_bench/timeseries.py
DOC: remove non-existent parameter from ExcelFile docstring #2613
BUG: nanmin/nanmax fails for empty int dtype #2610
BUG: fix unit test on linux where too many slashes in file://. close #2564
BUG: fix groupby bug/segfault with NAs in hierarchical level. fix MultiIndex tuple with NA issue. close #2616
BUG: unstacking int64 overflow with many levels. re #2616
BUG: fixed old version compatibility warnings
     added copy_to method to allow file upgrades to new version
didn't include the test file (in _static of docs dir)
DOC: minor doc updates to conform with new datetime64 behavior
DOC: release notes formatting fixup
BUG: updated the copy method to work with supplied options
ENH: added overwrite parameter to copy (defaults to True)
ENH/BUG: refactor of non-table HDFStore to put in object form (Storer class), for future enhancements
         added shape to non-table display
         closes GH2637
TST: more tests, added ncols to table output in printing
BLD: rebased - for some reason was not up to date