Use kebab-case in test function names
Use kebab-case in test function names

Test function names with underscores have been deprecated in favour of their
kebab-case variants. The deprecated form will be removed in Rakudo 2015.09.
This change brings the test suite up to date with current Rakudo.

tadzik/JSON-Unmarshal,sergot/JSON-Unmarshal,tadzik/JSON-Unmarshal