Make decimals uint8 in token example

[frangio]

The decimals variable should be uint8 according to ERC20 spec. https://github.com/OpenZeppelin/zeppelin-solidity/blob/f45a4e824363718fc625c519cc3db9268a7263ab/contracts/examples/SimpleToken.sol#L17

[androolloyd]

I have fixed this as apart of: #405

[androolloyd]

this ticket can be closed, i didn't reference the issue when committing, or in my PR, sorry about that.