ENH: add display.max_seq_items to limit len of pprinted long sequences
TST: add test for com.is_sequence
Merge remote branch 'y-p/feature/limit_printing_long_seq'

* y-p/feature/limit_printing_long_seq:
  TST: add test for com.is_sequence
  ENH: add display.max_seq_items to limit len of pprinted long sequences
DOC: update release.txt with display.max_seq_items option
BLD: update tox.ini, replace py3.1 with py3.3
BUG: fixed value_counts with datetime64[ns], GH 3002

TST: added test_datetimeindex formats with NaT