running on node >=6.x, new dependency installation tree breaks compatibility

[Jaxolotl]

Hi, since the new way to determinate the tree position on the node_modules installed packages has changed, the dependency on selenium-webdriver might break in some cases (e.g another package installing an unsupported higher version )
by changin "selenium-webdriver": ">=2.33.0",into "selenium-webdriver": ">=2.33.0 <3.0.0", it will install the snested dependency if in conflict with other installed package ( I tested with selenium-webdriver v2.52.0 and worked perfectly)