This patch makes Page.evaluate await promise if one is
returned by the evaluated code.
This makes the Page.evaluateAsync unneeded, so the patch
removes it.
Fixes#11.
The PhantomJS has a similar callback called onInitialized. This
callback passes control to the automation script when the page
gets initialized.
To precisely implement this functionality atop of puppeteer,
and since puppeteer controller script lives in a separate process to
the page, we need an ability to pause page at the moment of
initialization. For now, we are not able to do this.
However, oftentimes clients want to evaluate certain code in
page at the point of page initialization. This patch implements
this capability with the Page.evaluateOnInitilized method call.
This patch also re-implements phantom's unrandomize.js example
with the puppeteer API. This is serves an illustration purpose
for the page.evaluateOnInitilized callback.
