0.17.0

• (breaking change) Macro defs are now parsed like regular methods. Enclose the body with {% begin %} .. {% end %} if you needed that behaviour
• (breaking change) A union of two tuples of the same size results in a tuple with the unions of the types in each position. This only affects code that later tested a tuple's type with is_a?, for example tuple.is_a?({Int32, String})
• (breaking change) Method arguments have now a different semantic. This only affects methods that had a splat argument followed by other arguments.
• (breaking change) The syntax {foo: 1, bar: 2} now denotes a NamedTuple, not a Hash with symbol as keys. Use {:foo => 1, :bar => 2} instead
• The syntax exp as Type is now deprecated and will be removed in the next version. Use crystal tool format to automatically upgrade your code
• The compiler now gives an error when trying to define a method named !, is_a?, responds_to?, nil?, as or as?
• Added the NamedTuple type
• Added double splatting
• Added external argument names
• Macro defs return type is no longer mandatory
• Added as?: similar to as, but returns nil when the type doesn't match
• Added Number::Primitive alias
• Added Tuple#+(Tuple)
• Added ArrayLiteral#+(ArrayLiteral) in macros
• Crypto::MD5 now allows Slice(UInt8) and a block form (thanks @will)
• Added docs for XML (thanks @Hamdiakoguz)
• Many bug fixes