Expose keep-alive connection param

lib/connection-parameters.js

@@ -59,6 +59,7 @@ var ConnectionParameters = function(config) {
   this.client_encoding = val("client_encoding", config);
   //a domain socket begins with '/'
   this.isDomainSocket = (!(this.host||'').indexOf('/'));
+  this.keepAlive = config.keepAlive || false;
 
   this.application_name = val('application_name', config, 'PGAPPNAME');
   this.fallback_application_name = val('fallback_application_name', config, false);