bsToHex now returns String instead of ByteString
Fixing display issue with ScriptOp Show instance
add missing opcodes for Script.hs

- include all operations documented on bitcoin.it/wiki/Script

- remove instance Show ScriptOp due to verbosity (maybe there is a better way
  using generic-deriving)

- manual data entry, lacks tests
add missing opcodes to Abritrary.hs, add put OP_IF
add testEncodeDecode x

verify (decode (encode x)) == x