0.5.0

This is a full rewrite of the entire project. This version is a
candidate to become the 1.0 version.

We advise to take a look at:

• the new documentation online,
• the collection of examples.

Shortly, here are the new types the extension provides:

• Store, which holds the engine, the compiler etc.
• Module, which represents a Wasm module, with validate, new,
  name=, name, exports, imports, custom_sections,
  serialize and deserialize,
• Instance, which represents a Wasm instance, with new and
  exports,
• Exports, which represents a collection of exported entities, with
  respond_to_missing?, method_missing, and length,
• ImportObject, which represents a collection of imports that will
  be passed to Instance, with new, contains_namespace, and
  register,
• Function, which represents an imported or exported function, with
  new, call and type,
• Memory, which represents an imported or exported memory, with
  new, type, size, data_size, grow, + memory views that
  extends Enumerable,
• Global, which represents an imported or exported global, with
  new, mutable?, value, value=, and type,
• Table, which represents an imported or exported table, with new
  (small API for the moment),
• Type, FunctionType, MemoryType, GlobalType and TableType,
• ExportType and ImportType,
• Value which represents a Wasm value,
• Wasi module, which provides the Version, StateBuilder and
  Environment classes.

Added

• Online documentation, with tested examples
  (#51 by [@Hywan])
• Tests run against Ruby 2.7 + 3.0, and against Linux + macOS
  (#49 by [@Hywan])

Changed

As we said, the extension has been fully rewritten, and the code is
likely to not be compatible anymore. Here are the most notable
patches:

• The big rewrite
  (#48 by @Hywan)
• Remove Ruby dependency to rutie
  (#52 by @Hywan)