Node.js support

Added node.js support

var openpgp = require ('openpgp.js').openpgp;
openpgp.init();

things that work:
	reading public key
	reading private key
	decryption using private key

things that need work:
	key generation (not really tried this, not sure how entropy is generated in node)
	encryption using public key (a message is generated, but decryption of it fails)