fix(cli): convert capabilities arguments to dot-notation for WebDrive…

…r compatibility

lib/cli.js

@@ -83,6 +83,22 @@ if (argv.exclude) {
   argv.exclude = processFilePatterns(argv.exclude);
 }
 
+// WebDriver capabilities properties require dot notation.
+var flattenObject = function(obj) {
+  var prefix = arguments[1] || '';
+  var out = arguments[2] || {};
+    for (var prop in obj) {
+      if (obj.hasOwnProperty(prop)) {
+        typeof obj[prop] === 'object' ? flattenObject(obj[prop], prefix + prop + '.', out) : out[prefix + prop] = obj[prop];
+      }
+    }
+  return out;
+}
+
+if (argv.capabilities) {
+  argv.capabilities = flattenObject(argv.capabilities);
+}
+
 ['seleniumServerJar', 'chromeDriver', 'onPrepare'].forEach(function(name) {
   if (argv[name]) {
     argv[name] = path.resolve(process.cwd(), argv[name]);