Enabled opus codec by default

Ignore-this: cf16c0832038672bd117c26f08ed3cd6

darcs-hash:20130711115615-56b4d-7a97b15e5a4f87d2d4284dff700a931b55e1ab09
Simplified fetching the relative uri for a document

Ignore-this: b6764362ef86458e31e936669d56b878

darcs-hash:20130715100905-b22ec-27f636e5d5456c15b490f7a4c6963444b4472172
Renamed variable for clarity

Ignore-this: 822fca9137cf3328e657859eade3cf5

darcs-hash:20130715102525-b22ec-2ea66c628d81db995d2f8c419768fe68ea3136d1