Expose logout*.

This makes it easier to integrate logging out with Noir.
Modified the method of setting default values in cemerick.friend/authenticate*
Updated Ring URI
refer to `identity` properly
fix travis config
Tweaks to handle authorization failures more correctly (motivated
by discussion on gh-19):

* :unauthorized-redirect-uri is no longer used (was nonsensical)
* additional data may now be added to the stone thrown upon unauthorized access
* that data is now added to the request passed to :unauthorized-handler
* tweaks to keys for consistency
Use HTTP 401 instead of 403 to indicate unauthorized authenticated request, fixes gh-20
Merge branch 'expose-logout' of https://github.com/jszakmeister/friend

Conflicts:
	src/cemerick/friend.clj
http-basic workflow now properly responds with www-authenicate challenge when no credentials are provided, fixes gh-16
Only emit www-authenticate challenge from http-basic workflow if (not :allow-anon?), ref gh-16
OpenID workflow's :max-nonce-age now specified in ms, not seconds
Use a core.cache TTL cache to avoid storing unprintable DiscoveryInformation objects in the ring session, ref gh-10, gh-11
add changelog
release 0.1.0
fix changlog formatting
set clojars as "releases" deployment repository
0.1.1-SNAPSHOT
add support for credential function to return maps with custom password key
ignore pom.xml*
Allow ::redirect-on-auth? to be a string indicating the URI to redirect
to