Opcode generation isn't python3 compliant

When using the latest version of yargen with python3 I found that opcodes were being added incorrectly. The opcodes included the python indicator for byte strings `b''`:

Example:
```
 $op0 = { b'595f5f5e5b8be55d51c3cccccccccccc' }
```

Likely due to an issue on this line not encoding the byte string as utf8:
https://github.com/Neo23x0/yarGen/blob/master/yarGen.py#L1641

