TST: ensure Period.strftime returns Unicode
BUG: Period.strftime should return unicode strings always GH3363
BUG: sort out unicode/str/repr and py2/3 for Period Objects GH3363

PTF
Merge pull request #3409 from y-p/GH3360c

BUG: don't rely on sys.getdefaultencoding if we don't need to
DOC: update RELEASE.rst
Merge pull request #3410 from y-p/GH3363

Period.strftime should return unicode strings always
DOC: update RELEASE.rst
BUG: fix df repr troubles GH3337
ENH: add internal get_default_val() function to core.config
ENH: add helper for detecting any IPython zmq frontend, make in_qtconsole robuster
BUG: Always Ignore auto-detect terminal size for qtc/+ipnb

this is ignored anyway unless the user sets width/height to 0,
but even then, size detection only works for proper terminals.
DOC: Add comments, tweak option descriptions.
CLN: convert test utilizing disp.line_width to disp.width
ENH: Adjust height/width/max_rows defaults to match informal survey results
TST: adjust tests to accommodate new defaults for display options
TST: fix test_repr_non_interactive passing by accident
BUG: for numerical option, sentry should be another Type, not 0
ENH: optimize _repr_fits_horizontal_, to_string only on slice of interest
BUG: rework get_console_size to handle cases properly
ENH: fix df.repr() for scripts (keep GH1611 away), accept None for max_cols/rows