Release 0.1.5

This release introduces curve encryption and decryption:

key_pair = ECCrypto.create_key_pair
private_key = key_pair[:hex_private_key]
public_key = key_pair[:hex_public_key]

encrypted_message = ECCrypto.encrypt(public_key, "secret message")
decrypted_message = ECCrypto.decrypt(private_key, encrypted_message)

A string message can be encrypted using a public key from the the curve. The encrypted message can then be decrypted using the corresponding private key.