added google event tracking to the generator

Verify:

- run gonzo with a local version of Beaker
- generate a sample site using `rails g beaker:marketing {new_page_name_with_underscores}`
- visit `/new-page-name-with-underscores`

Verify that tracking code is there. by inspecting these 2 js variables are set :point_down: 
```
window.lp.analytics.googleEventVariables
window.lp.analytics.trackValidSubmission
```