v1.2.0

Changelog

• 947eab1 Merge pull request #62 from JunNishimura/feature/add_return_break_continue
• 9c24c26 Merge pull request #63 from JunNishimura/feature/go_fmt
• d1ef100 Update README.md
• 151dbf5 add examples (#57)
• d49dab8 add object for break, continue and return (#57)
• 2b6d288 add unit tests for break, continue and return statements (#57)
• 09f0409 consider outer env when to set values to identifiers (#57)
• c1a2c5f gofmt all files
• 3b17ceb handle with break, continue and return exp in eval (#57)
• 0c4900b update README.md