v0.4.0

v0.4.0

• Add send and receive subcommands (#16).
• showkey now indicates if a key is the signing key (e.g. Public Key (your signing key): 043da...). This indication is shown on the Public key only, even though the private key is technically the key used for signing.
• Fix bug where keys wouldn't show up in showkey unless both private and public keys were in the store. Now showkey shows keys even if only public key is in the store.
• Update README to explain path relationship between chattervox binary and serialport.node native addon (#13).