Add 'Stanford Fancy' SoA template and logic

@jrbl - Stanford Fancy SoA changes

Includes fancy autoscale and centering code.

![stanford_soa](https://cloud.githubusercontent.com/assets/3364609/5308628/e1473810-7bcd-11e4-9d49-cae2b9af24cb.png)

Let's pull this out into a method up at the top near prettify_isodate, like:
```
def get_cert_date(calling_date_parameter, configured_date_parameter):
    if calling_date_parameter:
        date_string = "{0}".format(prettify_isodate(calling_date_parameter))
    elif self.issued_date == "ROLLING":
        generate_date = datetime.date.today().isoformat()
        date_string = "{0}".format(prettify_isodate(generate_date))
    else:
        date_string = "{0}".format(configured_date_parameter)
    return date_string
```

And then call that method here to set the local variable date_string, and also use that method to replace the date_string calculation in the other two stanford-tagged cert methods. While we're at it we should probably do the v1 and v2 certs as well, but I think they just use self.issued_date directly.