Sequential calls of encryption API (`encrypt`, `wrap`, and `dump`) result in nonce reuse

Versions of the package cocoon before 0.4.0 are vulnerable to Reusing a Nonce, Key Pair in Encryption when the encrypt, wrap, and dump functions are sequentially called. An attacker can generate the same ciphertext by creating a new encrypted message with the same cocoon object.

**Note:**
The issue does NOT affect objects created with Cocoon::new which utilizes ThreadRng.