chore(config): saucelabs requires tunnel identifier to be a string

Author: juliemr

lib/cli.js

@@ -33,6 +33,7 @@ var argv = require('optimist').
     alias('build', 'capabilities.build').
     alias('verbose', 'jasmineNodeOpts.isVerbose').
     alias('stackTrace', 'jasmineNodeOpts.includeStackTrace').
+    string('capabilities.tunnel-identifier').
     check(function(arg) {
       if (arg._.length > 1) {
         throw 'Error: more than one config file specified'