ERR: between_time should raise on non-timelike objects
from [SO](http://stackoverflow.com/questions/34207898/issue-selecting-data-between-time-from-dataframe-in-pandas-0-17-1/34214431#34214431)

so passing anything except `time` objects or strings should raise (might be a tad tricky as we don't have great time parsers, they all parse datetimelikes).

IIRC this was done for convenience at the time. But can lead to an unstatisfactory user experience.
