change gem version to non pre-release

A version like `0.1.4.20140907a` is considered a pre-release version.
So we yank and replace it with `0.1.4.20140907.1`.
Bank finder methods return empty array when argument blank (ref #6).

This affects `find_by_blz`, `find_by_city` and `find_by_bic`.

Notably `find_by_bic` does not return all ban records, when invoked with `nil`. To get all banks, use `BLZ::Bank.all`.