Add support for not using $_SESSION.

Not all client applications will want to use this, and there's no
reason to force them. This provides a simple way they can change
how the data storage is implemented, without needing to rewrite
the entire client class.

Change-Id: I794150b93d5200e14116774c7260db19eefe8c68
Break up client functionality to allow for other workflows.

Not all clients are going to want to have to be at the end of a
postback for their entire existence. This allows them greater
control of the login cycle, if they want.

Change-Id: Ie9d3b3383091594e976273a2965e4d81a52dbb41
Make it possible to specify the postback url.

Leaving the default in place, make it possible to specify a different
endpoint for the postback data.

Change-Id: Ibfbd41f8097e4f0bc7d896f48f1791b6bcbd2bad
Update to match the styling on the IDE login page.

This also more closely matches the rest of SR things.

Change-Id: Icd23316d26b4e4351234e3abd808a816569231e0
Flip things around so the server has keys, not the clients!

Change-Id: I3e021f816c9c60cb8768db6162cc1eb74be8a714
Fix whitespaces.

Change-Id: I4bf1bdbbde646c4c1467ec4e6da44663d901d5b7
Update the README

Change-Id: Ie6a0b7e979defa4efe725268264cef90d42e9309
Remove an invalid <p>.

It didn't even change how it looked.

Change-Id: If0d2f8d104e28932b2bef129c9389f2131a3aed0
Remove logout redirection from the client.

As this isn't a valid thing to do, it shouldn't happen. Add a comment
for implementers so they know they still need to call this.

Change-Id: I370f5e357bb66a0680b1838e6b4fb536aa279aac
Merge "Remove an invalid <p>."
Merge "Remove logout redirection from the client."
Remove redundant JS usages.

These are all libraries, so removing them has no effect.

Change-Id: I36cbf5eda914159b598cac40ecbb20ccca493673
Merge "Update to match the styling on the IDE login page."