erc20 interface been broken

symbol & name of the token should be defined as a string, but you defined as byte32, which breaks the erc20 interface.

so when I use the standard erc20 interface to unpack dstoken, I get errors

```
abi: cannot marshal in to go slice: offset 35000214728014336407470934256024915466671168103574785725052718905953538277408 would go over slice boundary (len=32)
```

you can refer to this token contract(mkr): https://etherscan.io/address/0x9f8f72aa9304c8b593d555f12ef6589cc3a579a2#code