Added pytz to requirements/base.txt

Added the latest version of pytz (2014.7) to requirements/base.txt to
avoid errors with DateTime fields.
Added database credentials and security check for db password.

Added database credentials (user name: 'django', password: 'blank') and
security check for db password. The security check will raise an error
if the database password is 'blank' in production.
Fixed missing @ before db name.
Added the latest version of pytz (2014.7) to requirements/base.txt to
avoid errors with DateTime fields.
Merge pull request #138 from berndca/feature/pytz_requirement

Feature/pytz requirement