Made sure all exported types do have a typespec is useful in build scenarios
where the erlang compile options
[warnings_as_errors, warn_missing_spec]
are used.
A few type errors found by Dialyzer are corrected too.
modified: src/jsx.erl
modified: src/jsx_config.erl
modified: src/jsx_config.hrl
modified: src/jsx_decoder.erl
modified: src/jsx_parser.erl
modified: src/jsx_to_json.erl
modified: src/jsx_to_term.erl
modified: src/jsx_verify.erl
