Reduce redundant code

In the initial 0.1.0 version, a lot of code for both serialization and deserialization ended up being very similar. It would clean things up significantly to reduce code duplication, possibly by declarative macros and combining some `Serializer`s or `Deserializer`s together (for example, I believe there are a couple `Deserializer`s that are just for identifiers, which could be combined into a single `Deserializer`).