v2.6.0

• New Feature
  • declare API: recursive and mutually recursive types (thanks @utaal)
  • typescript definition file, fix #160 (thanks @DanielRosenwasser)
  • t.struct.extend, fix #164 (thanks @dzdrazil)
• Internal
  • split main file to separate modules, fix #158
  • add "typings" field to package.json (TypeScript)
  • add predicate field to irreducibles meta objects
• Documentation
  • revamp docs/API.md
  • add "A little guide to runtime type checking and runtime type introspection" (WIP)