Add support for custom window.open settings

[amercier]

This RB adds support for custom window.open settings:

PromiseWindow.open(url, {
  ... // width, height, etc.
  window: {
    scrollbars: false, // true by default
  }
});  

Fixes #9.

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Warning: beware that most settings have been disabled in modern browsers, for accessibility reasons. As far as I know only scrollbars works as intended.

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See window.open documentation on MDN for more details.

[coveralls]

Coverage increased (+0.2%) to 98.261% when pulling eee7717 on more-options into 9c369e7 on master.

[coveralls]

Coverage increased (+0.2%) to 98.261% when pulling 007f3fd on more-options into 9c369e7 on master.

[amercier]

Released in v1.1.0.