update signInButton CSS for new 123done design
Merge pull request #3848 from jrgm/fix-locators-for-new-123done

update signInButton CSS for new 123done design
adding /wsapi/realm_info?realm=foo.com
realm support in watch()

This adds realm support to Persona, specifically using the watch() api.

Realms allow a group of sites to state they are connected as part of a
group,
and if a user logs into 1 site of the group, or realm, the user should
be logged
into all the sites in realm.

This can be done by passing an extra parameter to watch():

navigator.id.watch({
realm: 'http://realm.123done.org'
});

The second part of the puzzle is that the watched realm must publish a
well-known file describing everyone that is part of the realm.

GET http://realm.123done.org/.well-known/browserid-realm
{
realm: ['http://foo.123done.org', 'http://bar.123done.org']
}

If the site's origin is found in the list of the realms found at the
well-known file,
then Persona will believe it is part of the realm. If a user had logged
in to
foo.123done.org, and then visited bar.123done.org, and that site also
watches
the same realm, the user will be automatically logged in upon page load.