release: v0.3: new macros, pattern matching, performance.

All user macros now do pattern matching on argument, including:

• named optional argument that may appear out of order.
• matching rigid required values.
• variadic arguments with &rest syntax
• match against lists containing named arguments (essentially hashmaps)
  and nested variadic &-syntax.

Added new macros:

• %apply
• %lambda
• %list
• %splat
• %strip
• %join
• %filter
• %map
• %embed
• %namespace
• %raw
• %string