Added Tree Parsing

Added a module for parsing the JSON AST into Haskell’s tree type,
because it’s much easier to move it back to a JSON value than the map
structure I had been using
Started work on TreePatch

Copied code from MapPatch and changed imports a bit - let’s see where I
can go with this
Added Remove and Add to TreePatch

First two Patch operations are ready!
Updated cabal file to accommodate new modules