Add support for reloading the page with a response attribute.

Now, a response with the `reload` attribute will trigger a reload.  The
attribute value should be a boolean, as follows:
```json
{
  "reload": true
}
```

Closes #103.
Merge pull request #109 from nicksay/reload

Add support for reloading the page with a response attribute.
Ensure the spf.process API function works.

Add a dedicated function to process a SPF response on the current page outside
of a navigation flow.  Export it as the `spf.process` function.

Closes #108.