Release 0.98

Bug fixes:

• Fixes the noexcept specification (required for Visual Studio 2015 and later.) Fix
  contributed by Rupert Steel.
• Fixes bug with proxy operator== when comparing object member values,
  such as in val["field"] == json("abc")

Enhancements:

• Refines error codes and improves error messages
• Renames json_reader method read to read_next, reflecting the fact that it supports reading a sequence of JSON texts from a stream. The
  former name is deprecated but still works.
• Adds json_reader method check_done that throws if there are unconsumed non-whitespace characters after one or more calls to read_next.
• Adds getter and setter max_depth methods to allow setting the maximum JSON parse tree depth if desired, by default
  it is arbitrarily large (limited by heap memory.)
• Modifies json static methods parse_string, parse_file, and parse_stream behaviour to throw if there are unconsumed non-whitespace characters after reading one JSON text.

Changes to extensions:

• Changes the top level namespace for the extensions from jsoncons_ext to jsoncons, e.g. jsoncons_ext::csv::csv_reader becomes jsoncons::csv::csv_reader
• Modifies csv_reader and csv_serializer so that the constructors are passed parameters in a csv_parameters object rather than a json object.
• Supports user defined header names for columns in CSV files