Added health_check.utils.healthcheck

Added a decorator that makes it a lot easier to write checks. Inside the
decorator you can raise health_check.utils.HealthCheckFailed or
health_check.utils.HealthCheckUnavailable instead of returning
status values.
The decorator optionally accepts a string with a descriptive name of the
check.
Merge branch 'master' of git://github.com/KristianOellegaard/django-health-check
updated docstrings, removed custom exceptions
fixed @healthcheck decorator
return True
Merge branch 'master' of git://github.com/ojii/django-health-check
Removed default return, you should explicitly do that
Added LICENSE file