uncaughtExceptions from underlying pg module should be handled and passed as errors

I've noticed for certain classes of error (e.g. db connection string not provided; db connection failed), the module surfaces uncaughtExceptions which can only be handled by the process.on('uncaughtException') stuff from Node.  Seems logical that these things could be  handled and passed up as a regular error in the callback, rather than crashing the whole application.
