(chore) hello_world testing
Merge remote-tracking branch 'remotes/upstream/master'
Merge remote-tracking branch 'upstream/master'
(fix) Add more invalid input type testings for hello_world, especially 'undefined' that may lead to test failure
Merge remote-tracking branch 'remotes/upstream/master'
Merge branch 'master' of https://github.com/itga/lightning-katas
(chore) Using 'undefined' in stead of 'typeof null'
(chore) add the invalid_example to be display if the test fails
Merge pull request #7 from itga/master

(chore) hello_world error handling