Add blur validation to free trial form

The old PPC landing page validating the required fields on blur in addition to submit. This adds the validation for each required input on the blur event as well as the submit event to the new form.

To test, load the /free-trial page. Then focus into the `url-input`, `name`, and `email` fields. For `url-input` and `name` enter nothing and then trigger the blur event. For `email`, enter an invalid email. If all fields are invalid after blur you should see this:

![screen shot 2014-12-09 at 3 58 36 pm](https://cloud.githubusercontent.com/assets/150579/5365752/78eeb476-7fbc-11e4-9aff-62cbdececa44.png)