createRandomSecp256k1Key returns a null key

[cnorburn]

Code located in the CasperKeyHelper

[meywood]

The key for Secp256k1Key is a big integer so really would need a big refactor perhaps with generics. In the mean time the secp256k1PrivateKey.getKeyPair().getPrivateKey() should be used.

[meywood]

Will be resolved once PR against PR syntifi/crypto-keys#12 is approved and merged

[meywood]

Closed in issues/63