Review: WebView tests and Command Line Arguments [fixes #4]

[spolu]

This adds an options object as second argument to the main function that can take an args dictionary and a custom exec_path string.

// test.js
require('node-thrust')(function(err, api) {
  // ...
}), {
  args: {
    "show-fps-counter": true
  },
  exec_path: '...'
});