Deserializer should not check correctness of data, this is the respon…

…sibility of the Visitor

Examples of errors produced during deserialization of internally tagged enums in tests
if instead of a Seq/Map a Str("unexpected string") will be provided:

In tests/test_annotations.rs
  flatten::enum_::internally_tagged::tuple:
    before: `invalid type: string "unexpected string", expected tuple variant`
    after : `invalid type: string "unexpected string", expected tuple variant Enum::Tuple`

  flatten::enum_::internally_tagged::struct_from_map:
    before: `invalid type: string "unexpected string", expected struct variant`
    after : `invalid type: string "unexpected string", expected struct variant Enum::Struct`