figure out way to have scrapers work for gated resources behind proxies

[dcohen]

the url, e.g., for GMU's gated resources remains mutex.gmu.edu/login so there's no way to know what resource is being used

[simon]

(In [273]) Addresses #68, figure out way to have scrapers work for gated resources behind proxies. We can now access pages through an EZProxy. We need to know what alternatives to EZProxy exist in order to support them. Also, fixes some spacing issues in browser.js.

[simon]

(In [308]) closes #68, figure out way to have scrapers work for gated resources behind proxies. most institutions use EZProxy for their proxy needs (or a more transparent proxy, which we support natively). this implementation is significantly better than the old one, which refused to work after you'd already logged in once, and is also simpler, because it's stateless. it has to observe every HTTP request, but there's no noticeable speed hit. it also still doesn't work when there's a link from one gated site to another gated site, but as far as i can tell, this only happens on the Gale Group site.