Change a MAY to SHOULD as a non-standard impl really should revert if a contract doesn't accept 1155's.

EIPS/eip-1155.md

@@ -346,7 +346,7 @@ To be more explicit about how the standard `safeTransferFrom` and `safeBatchTran
  - It MUST NOT consume more than 5,000 gas.
 
 **_Implementation specific transfer API rules:_**
-* If an implementation specific API function is used to transfer ERC-1155 token(s) to a contract, the `safeTransferFrom` or `safeBatchTransferFrom` (as appropriate) rules MUST still be followed if the receiver implements the `ERC1155TokenReceiver` interface. If it does not the non-standard implementation MAY revert or MAY proceed. 
+* If an implementation specific API function is used to transfer ERC-1155 token(s) to a contract, the `safeTransferFrom` or `safeBatchTransferFrom` (as appropriate) rules MUST still be followed if the receiver implements the `ERC1155TokenReceiver` interface. If it does not the non-standard implementation SHOULD revert but MAY proceed. 
 * An example:
  1. An approved user calls a function such as `function myTransferFrom(address _from, address _to, uint256[] calldata _ids, uint256[] calldata _values);`.
  2. `myTransferFrom` updates the balances for `_from` and `_to` addresses for all `_ids` and `_values`.