IV for AES-GCM must be 96 bits, not 64

[Vladimir Dzhuvinov]

Plaintext Encryption with AES GCM says the initialisation vector must be 96 bits:

http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-08#section-4.9

Our current implementation has a 64-bit IV:

https://bitbucket.org/nimbusds/nimbus-jose-jwt/src/46b99f696858/src/main/java/com/nimbusds/jose/crypto/RSAEncrypter.java?at=master#cl-131

[Vladimir Dzhuvinov]

Fixed in commit c9525a3