Handle JSONP correctly

The JSONP wrapper should not be cached by RABL. The workaround is described here: https://github.com/nesquena/rabl/issues/548. Also added tests that behave as expected.

This closes https://github.com/articlemetrics/alm-report/issues/35. 
Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping.