Refactor Encoders and add JSON support

[erikgaal]

Builds upon #83 and refactors it a bit to provide a clear solution. Also rebased the PR so it's up to date with the trunk.

Thanks @lsmith77 for the original PR!

[nonoesp]

Hi, @lsmith77 and @erikgaal I don't have the bandwidth to take on new features and maintain this project.

Would any of you want to help?

These pull requests are a really good start; it's just that I haven't even had time to figure out whether there are parts that break with your changes.

[CoolGoose]

@nonoesp since we're starting to use this more in our company, is there something I can start helping with to review / add tests so we can get some of these things moving forward ? Json support is something we're going to need, and I think it would be nice to do it part of this and not a fork.

[nonoesp]

@CoolGoose Hey! I have limited bandwidth for this. But I'll be happy to chat and let you maintain this package if you'd like. =)

[CoolGoose]

I can give it a try since I should be able to have a few hours per week for this. Let me review this PR first, and see how this goes ;)