DOC: release notes corrections

TST: argmin/max impl, tests, and doc-strings
API: raise on __nonzero__ for Index (GH7897)
Merge pull request #7951 from jreback/index_follow

DOC/TST: index followup
ENH: New `level` argument for DataFrame.tz_localize and DataFrame.tz_convert (GH7846)
Merge pull request #7915 from mtrbean/ENH-7846

ENH: New `level` argument for DataFrame.tz_localize and DataFrame.tz_convert (GH7846)
CLN: change requirements to only use numpy>=17
CLN: remove constants from pandas toplevel
CLN: remove np16 checking from setup.py
CLN: no more suprimo generic.py hacks
CLN: grouby facelift
CLN: down with np16 internals
CLN: ops no more pasta
CLN: pytables timdelta goodbye timmy
CLN: remove skipping np17 from testing
CLN: do not skip np17 in tests
CLN: offsets are now always nano np16 no moar
CLN: remove extremo hack to get around np16 hell
CLN: remove lots of conditionals from tslib.pyx from np16