format detection confused by extname appearing in basename

[seamusabshere]

format auto-detection is bad because it doesn't start at the end when looking for extnames:

foo.csv -> detected as csv
foo.xls -> detected as xls
fooxls.csv -> detected as xls (WRONG)

it should probably choose the format whose extname has the highest rindex

it should probably keep looking in the basename, otherwise we won't be smart about filenames like "foo_xlsx" which to a human is obviously an xlsx.

assigning to @activefx in case he's got time

[seamusabshere]

simpler and better to use \z than what i suggested (rindex) - thank you!

please add to CHANGELOG

[activefx]

No problem. Does it go under 2.1.1 as a bug fix? Should I update the corresponding date to today?

[seamusabshere]

i use a manual version bump / tag / release process - check out 63db4bc - all done for now