browserify includes browser-compatible versions of many of the modules from
node core such as: url, path, querystring, events, stream, util and more!
This means that many modules written for node without the browser in mind
will just work.

For this level, `prompt()` will return a web address.
Parse the address's query string and print the "file" parameter from the
query string relative to the rest of the web address.

For example, this address:

  http://substack.net/filez/dogez/img.cgi?file=../hi/doge.gif

should print:

  http://substack.net/filez/hi/doge.gif

Instead of using a hand-rolled parser, there are some very handy functions
from node core you can use from the url and querystring modules.

* url.parse(addr) takes a web address string and returns an object with all
the components of the url. In particular you will want the "query" property
from the result.

* url.resolve(baseAddr, path) resolve the `path` string with respect to the
baseAddr url.

* querystring.parse(str) takes a querystring string `str` and returns an
object mapping querystring keys to values

Just `require('url')` and `require('querystring')` to get each of these
modules. You don't need to run `npm install` for url or querystring because
they are built into browserify similarly to how they are built into node.

Compile your program with `browserify` and pipe the bundle into
`$ADVENTURE_COMMAND verify` like this:

  browserify main.js | $ADVENTURE_COMMAND verify

If you just want to run your solution with the test input without verifying
it you can do:

  browserify main.js | $ADVENTURE_COMMAND run