Aly Cerruti

Allow for supplying custom encoders to ScalaPB ones

1

For example, the API I'm using requires me to send `Map[String, A]` as `{"key": $string, "value": $a}` and not `{$string: $a}`. I've created a custom `Map[String, A: Encoder]` to do...

Conforms to the general circe naming scheme. Also uses proper package naming.