Big rewrite of internals. Completely breaks API.

Most of the test (that used to work) are working again.

* Internal data structure can facilitate 'Table Arrays'.
* Moved from TOML to Toml (less shouting).
* Renamed all types to most closely match the TOML spec.
* Structuring moved from 'main' to Parser and Types.
* Added types for restricting the array to only contain same-typed
  items (not yet implemented though).