Force correct handling of query string parameters.

mikeal/request does not appear to handle array parameters the same way
as default node.js querystring.stringify.

Given the parameters {foo: [1, 2, 3]}, it generates the querystring
foo[0]=1&foo[1]=2&foo[2]=3 insteadd of foo=1&foo=2&foo=3.

Our API expects the latter, so we need to use querystring.stringify to
handle this and build the full url ourselves.