* This is step toward implementing #14 in that it shows you a list of the items
which need to be crafted. However, it still doesn't show you the steps and
proper order in which to craft everything.
* Update page title when changing items
* Update page URL to reflect proper url when changing items
* Send another pageview to Google Analytics after changing the page
* If a "tool" is also a raw material (e.g., as a "cow" is for producing milk),
be sure to add it to the inventory so that it shows up as one of the outputs
* Re-write the `computeMissingResources` method to be `craft` and refactor how
it performs calculations to be easier to follow, and to avoid several errors
in the prior calculation related to recipes which produce more 1 quantity of
the output items.
Andrew Miner