Fix "phantomjs.binary.path" configuration

Before this fix, I ended up with the following exception:

Caused by: java.lang.IllegalStateException: The path to the driver executable must be set by the phantomjs.binary.path capability/system property/PATH variable; for more information, see https://github.com/ariya/phantomjs/wiki. The latest version can be downloaded from http://phantomjs.org/download.html