0.20.1

• (breaking change) Set#merge as renamed to Set#merge!
• (breaking change) Slice.new(size) no longer works with non primitive integers and floats
• (breaking change) The macro method argify was renamed to splat
• Added pretty printing. The methods p and pp now use it. To get the old behaviour use puts obj.inspect
• Added ArrayLiteral#[]=, TypeNode#constant, TypeNode#overrides? and HashLiteral#double_splat in macros
• Added a finished macro hook that runs at the end of the program
• Added support for declaring the type of a local variable
• Added Slice.empty
• Flags enums now have a none? method
• IO::ByteFormat has now methods to encode/decode to/from a Slice
• Spec: the line number passed to run a specific it block can now be inside any line of that block
• The CallConvention attribute can now also be applied to a lib declaration, and all funs inside it will inherit it
• The method_missing hook can now define a method, useful for specifying block arguments
• Support double splat in macros ({{**...}})
• Some bug fixes