Update comments that had false information
Add new base64 serializer
Set new Base64Serializer as default on CookieProfile

The previous standard was the JSON serializer, however with upcoming
changes that limit what characters are allowed in cookies, bare JSON no
longer worked because it could return values that are invalid to be
stored in cookies.
Raise ValueError if cookie value has invalid chars

WebOb will now raise a ValueError if an attempt is made to set the
cookie to an invalid value. According to RFC6265 a cookie-octet has a
specific subset of allowed ASCII characters, and that subset does not
change whether the value is DQUOT'ed or not.

WebOb will still accept all other cookies, it just won't be able to
create them.
Document cookie name requirements explicitly
Import assert_raises
Remove utf-8 strings from testing
Update test strings to match what is now returned
Verify decode of old cookies, and failure of encoding same cookies
Remove useless test
Add new test for CookieProfile

We want to make sure we have at least one test for CookieProfile that
fetches a cookie from our request object, and then verifies it returns
the appropriate answer.