Sanity check node-webshot options

[rosskukulinski]

After skimming the node-webshot docs, I think we may want to enable a few of these options:

• errorIfStatusIsNot200
• timeout

We may also want to use some other callbacks to get additional functionality related to page load times and number of resources requested.

https://github.com/ariya/phantomjs/wiki/API-Reference-WebPage#webpage-onLoadFinished
https://github.com/ariya/phantomjs/wiki/API-Reference-WebPage#webpage-onResourceRequested
https://github.com/ariya/phantomjs/wiki/API-Reference-WebPage#webpage-onResourceReceived