PERF: perf regressions on insertion of columns into frame (related to 4032)

PERF: vbench for inserting cols at the beginning
Merge pull request #4057 from jreback/insert_columns

PERF: perf regressions on insertion of columns into frame (from GH4032)
TST: add test for DataReader class
TST: add read_google test
TST: use builtin equality testing
CLN: use a temporary zipfile
BUG: make the pause nonzero but short
CLN: give everything that needs it a closing context manager
CLN: clean up the testing suite
BUG: do not dropna unconditionally
TST/BUG: print out month and year because they are making lxml fail