COOK-2330: use String#upcase in celeryconfig.py.erb

I'm not sure how (or if) this ever worked before, as String#upper
doesn't seem to be a valid method.
COOK-2337: expose supervisor_service environment attribute on gunicorn and celery lwrps
COOK-2337: using merge instead of merge!
COOK-2337: default environment attrs to {}
Merge pull request #18 from needle-cookbooks/COOK-2337

COOK-2337: expose environment attribute on gunicorn and celery submodules
Merge pull request #17 from needle-cookbooks/COOK-2330

COOK-2330: use String#upcase in celeryconfig.py.erb
doc environment parameter, celery sub-resource
[COOK-2403] Cast symbol to string in templates

Cast the cookbook_name symbol to a string, so that the gunicorn_config
and template resources being created work if a custom template is
provided.
Merge pull request #19 from rcloran/master

[COOK-2403] Cast symbol to string in templates