modify internal arguments handler

wandbox-build-request-data takes keyword arguments.
it is same as wandbox-compile.

for example:
(wandbox :lang "ruby" :code "p 'HELLO'")
;=> run on wandbox
(wandbox-build-request-data :lang "ruby" :code "p 'HELLO'")
;=> return JSON string for passing wandbox API

add sync keyword (for experimental).

fix chagelog typo. #1