A few small enhancements...

A series of small changes which make the library (which is great, by the way!) usable for my purposes:
 * fire an event for exceptions in the processing thread, so that the caller can deal with them
 * deliver the :ready? promise a false value on exceptions, so that dereferencing it doesn't hang forever
 * add a (quit) fn so clients can quit without killing the connection
 * add simple SSL support to create-connection