Warn on confusing order of operations

[nhthn]

sclint should warn if it encounters a binary op that is a child node of another binary op. A possible exception is if both binary ops are the same and are either "*" or "+". I think requiring (3 + 4) + 5 over 3 + 4 + 5 is a bit much especially if e.g. mixing together signals in a SynthDef.