attr_set should allow boolean and numeric pass-through

[dheiman]

Attributes set via attr_set all end up being strings. However, when numerics and booleans are passed unquoted to the API, they will be set to their respective type. We should find a way to respect this, either by splitting attr_set into something along the lines of attr_bool_set, attr_str_set, and attr_num_set, or doing inference.

Even though I think the latter option is "prettier", the former seems the safest, especially if we alias attr_set to attr_str_set to maintain backwards compatibility, as it seems like configs will coerce type as able when input parameters are set to attributes.