Use the phantomjs-prebuilt module

[gwynjudd]

Resolves #53 and fixes the path to phantomjs mentioned in #66 in a better way

[dflynn15]

While I understand the desire to have Phantom as a part of the plugin I have kept away from including it for two main reasons.

First, it keeps this project tied specifically to a version of Phantom JS which I really do not wish to do. Tying the project down to specific versions will then lead to people asking for the option for other versions, etc. which in the end is not the focus of this plugin. I want people to be able to choose what they want with Phantom (version and all). If you want to get a beta version, go for it! If you want to use a deprecated 0.x sure, have fun! Ultimately, I want people to have options. Plus, it prevents anyone from having to potentially download yet another version of phantom because of versioning (i.e. grunticon and others).

Secondly, by expecting it globally and only looking for it in node_modules afterwards it gives the us the opportunity to not pull down a heavy npm package. There are many use cases where having long standing npm install scripts can crash servers, cost development time, and really just frustrate us all. In allowing the developer to "choose their own path" we can allow people to not have to include Phantom as a npm package but have it globally installed (faster npm install!!).

I'll open up another PR that allows for checking for the .cmd file like it previously did and we can go from there. Thanks so much for all your help on this!

[gwynjudd]

OK no worries