fix(deps): fix error on ci

Author: watilde

package.json

@@ -34,6 +34,7 @@
     "karma-firefox-launcher": "1.x || ~0.1.0",
     "karma-mocha": "^1.0.1",
     "karma-power-assert": ".",
+    "mocha": "^2.4.5",
     "power-assert": "^1.4.1",
     "rimraf": "^2.5.2",
     "standard": "^7.0.1",
@@ -48,4 +49,4 @@
   },
   "homepage": "https://github.com/watilde/karma-power-assert#readme",
   "license": "MIT"
-}
+}