Inline everything.
Added missing include for std::runtime_error
Corrected initialization order
Fix a signed / unsigned comparison warning with gcc
Remove debug log
Fix multiple definitions of spaces.
Differentiate between serializable and non serializable fields with the star operator:

  iod(*name = "test") -> to_json -> {"name": "test"}
  iod(name = "test") -> to_json -> {}

Add methods :

  auto o = iod( age = 12, inc = [] (auto& self, int a) { self.age += a; } );
  o(inc, a);
Merge pull request #1 from matt-42/master

sync from upstream