Support Autodiscovery

[kadamwhite]

Contains unit tests & integration tests, with ~85% coverage

Closes #74

The API this provides is as follows:

var apiPromise = WP.discover( 'http://my-site.com' );

apiPromise.then(function( site ) {
    // If default routes were detected, they are now available
    site.posts().then(function( posts ) { console.log( posts ); }); // etc

    // If custom routes were detected, they can be accessed via .namespace()
    site.namespace( 'myplugin/v1' ).authors()
        .then(function( authors ) { /* ... */ });

    // Namespaces can be saved out to variables:
    var myplugin = site.namespace( 'myplugin/v1' );
    myplugin.authors().id( 7 ).then(function( author ) { /* ... */ });
});

• TODO: Readme documentation

[kadamwhite]

🐎 doin it