use email as account username in default

[miurahr]

• Using email directly instead of hashing it. it is definitly equivalent things. Because 1:1 relation hash with email. Because cleaned_email in signup-form of account validate email as consist of characters that can be used as username.
• avoid try exception block when checking username.

Signed-off-by: Hiroshi Miura miurahr@linux.com

[paltman]

The problem with this is there are often email addresses longer than the default username field on auth.User.