Remove redundant self in user model function.
Remove redundant self in user model function.

References Coursemology/coursemology.org#179.

nnamon/coursemology.org,Coursemology/coursemology.org,nnamon/coursemology.org,Coursemology/coursemology.org,Coursemology/coursemology.org,allenwq/coursemology.org,allenwq/coursemology.org,dariusf/coursemology.org,allenwq/coursemology.org,nnamon/coursemology.org,Coursemology/coursemology.org,dariusf/coursemology.org,nnamon/coursemology.org,dariusf/coursemology.org,Coursemology/coursemology.org,dariusf/coursemology.org,dariusf/coursemology.org,nnamon/coursemology.org,allenwq/coursemology.org,allenwq/coursemology.org