Move Key Utils to separate gem

This release moves the key utilities to a separate gem, bitpay-key-utils.

MD5 Checksums

v2.4.4.zip 079bb2aff08dc5b89dc2faa8e0349891
v2.4.4.tar.gz 49dab3e4ff24d2f9dcfd71c6ff1701a2
bitpay-sdk-2.4.4.gem d96964066d9b76276ae25565ac71610b