Bills update

added validations to bill creations.
Bill validation over hall

created a custom validation for matching things that rails validation
aren't made for.

Added to check to make sure user_id, account_id, and payee_account_id
are real.

amount validation is a lot more robust.
I still don't allow things such as '$' or ',', because I don't want to
make a string parser.
Valid Options: 01234.56 or 0.56 or 12345
Invalid: 0.56789