Sandboxes can submit forms.

You need to set `sandbox.forms` to true when creating the
sandbox.

This relies on the HTML5 `allow-forms`.

```js
  var sandbox = Oasis.createSandbox({
    url: 'http://example.com/profile_viewer.html',
    capabilities: [ 'account' ],
    sandbox: {
      forms: true
    }
  });
```

[Fixes #4]
Merge branch 'allow-forms' into update-transpiler

Conflicts:
	dist/oasis.min.js