> Parenthesise this as || and && have the same priorty IRC. And I think it's bogus w/o them.

The code is a cut&paste of existing template constraints. All I did was put them in a template so I can use them from both the `put` and `opOpAssign` functions to avoid code duplication.

> Also how about add a test for appender of ints explicitly?

I didn't change any semantics, the operators simply forward to put functions.