Add an option to give a path to the PhantomJS executable

[medemi68]

Would it be possible to add an option to choose the path to the PhantomJS executable?

I plan on using a version of PhantomJS that is compiled for Linux ARM and I won't be able to use the phantomjs-prebuilt module.

If it's not possible to add one, could you perhaps set me in the right direction so that I can specify my own location?

[puzrin]

https://github.com/nodeca/navit/blob/3.0.2/lib/phantom/init.js#L22-L35

You can make PR with new option enginePath (and the same for electron).