Support for OpenId Provider Authentication Policy Extension 1.0

Initial support for OpenId PAPE.
 * Additional test case in openid_fast_tests.js
 * README updated to mention PAPE
 * The code itself is at the bottom of openid.js
 * sample.js now uses two example attributes.
Merge pull request #90 from jplyle/add-pape-extension

Support for OpenId Provider Authentication Policy Extension 1.0