Can't read excel decimal seconds
related to #4332

I have an excel spread sheet (.xls) that contains a time column. The time is displayed in Excel as minutes:seconds.tenths of seconds. Such as "50:59.2" "50:59.4". The raw data contains hours:minutes:seconds.decimalseconds.

It seems that Pandas uses xldate_as_tuple() which apparently rounds all seconds, so the decimal part is dropped.  So the above two data points both import as "50:59".  

I suggest  using a different conversion method, at least as an option.  That way the data will not be dropped, as it is now.
I did also post this same issue to xlrd.  
