BUG: Use Series.where rather than np.where in clip
Merge pull request #3998 from mtkni/series_clip_timestamp

BUG: Use Series.where rather than np.where in clip
CLN: remove isinstance(x, str) calls
CLN: pep8
CLN: remove redundant parens in conditionals
CLN: functions that take a sym argument should raise if the argument is not given
CLN: range -> xrange
CLN: remove backslashes
CLN: handle urls with context managers
CLN: use appropriate exception types
CLN: replace special method calls with their toplevel names
CLN: replace most empty exceptions with relevant exception types
TST: add test for DataReader class
CLN: pep8 test_google.py
CLN/TST: add tests for 99% coverage and PEP8
CLN: clean up and refactor
BUG: use correct context manager