break apart argonaut

[jdegoes]

• purescript-argonaut-core — Definition of Json, foldJson, and Eq, Show, Ord, etc., instances for Json, together with printing and parsing (which are native methods!). This will be a very small library with minimal dependencies, which other libraries can use to agree on what Json is.
• purescript-argonaut-combinators — All the combinators and operators that make using Argonaut easy. These, in turn, are largely defined in terms of the fold methods, but some may be special-cased for performance reasons.
• purescript-argonaut-serialization — EncodeJson / DecodeJson and instances for the world.
• purescript-argonaut-zipper — For things like JCursor, JZipper, etc. Maybe there's a better name for this one or maybe it belongs somewhere else.�

Thoughts?

[cryogenian]

Shall we make this repo aggregation like purescript-base?

[jdegoes]

Yes, this one should re-export the other modules in Data.Argonaut, and of course depend on them all in bower.