improve bytecode
- rename constant variable
- implements iterator execution
  - fix    iterator to return always [ value, index ]
  - rename Bytecode#__break__ -> Bytecode#break
  - add    Bytecode#setIterator
  - delete Bytecode#resumeWithIterator
- implements bytecode#yield
- implements Object#yield
- implements delay estimation
  - add Bytecode#push
  - add Bytecode#shift
  - add Bytecode#put
  - fix codegen
- add tests
- build v0.0.47
Merge pull request #61 from mohayonao/improve-bytecode

improve bytecode