Feature request: detect strict OOXML format and raise meaningful exception

[shitikanth]

As I understand neither fastexcel, nor POI itself support "strict ooxml" file format.
It would be helpful for the user to detect the ooxml format and raise an early exception like POI does.

Currently, the error raised to the user is like: Sheet#0 'sheet_name' is missing an entry in workbook rels (for id: 'null')
which is not very informative.

By way of contrast, the error raised by POI is: org.apache.poi.ooxml.POIXMLException: Strict OOXML isn't currently supported, please see bug #57699.