Login failures on URLs with characters needing URI-encoding

[alt36]

I'm using r4032login to automatically redirect to raven/login. If I have a URL with e.g. spaces, the login fails and hits https://github.com/misd-service-development/drupal-raven/blob/master/raven.module#L274 . By way of example, the following should be visible to anyone who has Raven-authenticated:

http://www.ch.cam.ac.uk/intranet/system/chemistry_raven_downloads/foo%20bar

but if one follows the above link, note that the &params= query param on the Raven login page is

&params=http%3A//www.ch.cam.ac.uk/intranet/system/chemistry_raven_downloads/foo%2520bar

so the % in the URI-encoded space looks to have been URI-encoded, mangling the URL. If you're not already logged in to Raven, this provokes a "Warning: Raven authentication failure."

Analysis will follow with a pull request shortly.