[openstack storage] properly URI encode container and object names

Rackspace container names can include any special characters except `/`, and object names have no restrictions. `pkgcloud` does not currently URL encode container or object names during requests, leading to unexpected results.

As an example,
````javascript
client.createContainer('foo!@#$%', function(err, container) {
        console.log(container);
});
````
will succeed and return a `Container` object with `name : "foo!@#$%"`, however it will actually create a container named `foo!@`.

I can create a PR for this, but would it go into `0.9.0` or `master`?