Add more tracking.

Adds more tracking to the SEO form to debug a reduction in new leads. Changes: 

1. Switches the API response time over to the GA user timing API instead of event tracking since user timing was made to track time
2. Makes the number of validation errors per submit easier to see in GA by storing it in the label value

*Verifying the user timing*:

Load /free-trial, open your network console (click preserve log), fill out the form, then filter your network requests for "collect". You should see an event that has these parameters: 

```
utc:api response time
utv:/account/free_trial_create
utt:24
```

utc = user timing category
utv = user timing value
utt = user timing time (this is the actual time so it will vary)

*Verifying the number of errors per submission*:

Submit the /free-trial form with bad data in one or more fields. Look for this event in the network log:

```
ec:form error
ea:seo-form validation error
el:3 errors
```

ec = event category
ea = event action
el = event label (if you didn't put anything in any of the fields you should see three, otherwise this number should match the number of validation errors you forced)