Allow passing of a randomBytes array that can be used to seed the generator

Possibility now exists to pipe in random bytes to the generator which can be used to create the entropy necessary to allow encryption.
The options object passed to adyen.createEncryption can now have a 'randomBytes' property containing an array holding these random bytes.
See: https://github.com/bitwiseshiftleft/sjcl/wiki/Symmetric-Crypto#seeding-the-generator.

Also look for presence of getElementsByTagName rather than typeof getElementsByTagName - allows encryption to work in IE8