fix sub (#586); add gsub/3; add transpose/0.

Signed-off-by: William Langford <wlangfor@gmail.com>
Properly call onig_error_code_to_str

Fix #585
Add support for JSON sequence MIME type

Per draft-ietf-json-text-sequence-07 (which soon will be published as an
RFC).
Fix #600.  Add regression test