another new dataset and some cleanup

Hey,

I've already added another data file for the upcoming BLZ cycle (2014/03/02–2014/06/08) and added some logic to read the correct file (depending on the current date). I also took the liberty to reflect the data-valid-until-date in the version number.

To minimize the gem size, I gzip'ed the data files and removed the Excel source files.

As bonus, there is now also a `BLZ::Bank.find_by_bic` method.

Grüße,
Dominik