Add: @@loop statement

[haoxins]

update md

update md

loop handler + data.json

update md

update md

update md

[coveralls]

Coverage decreased (-14.3%) to 82.54% when pulling 735eb98 on loop into 3a36590 on master.

[coveralls]

Coverage decreased (-14.3%) to 82.54% when pulling 9d888d6 on loop into 3a36590 on master.