allow rc file to contain location of config file

Author: Amos47

lib/commands/set-default-argv.js

@@ -128,7 +128,7 @@ module.exports = function(internals, isModule) {
 
   internals.argv = deepExtend(internals.argv.argv, rc('db-migrate', {}));
   internals.argv.rcconfig = internals.argv.config;
-  internals.argv.config = _config;
+  internals.argv.config = internals.argv.configFile || _config;
 
   if (internals.argv.version) {
     console.log(internals.dbm.version);