fixes :save internal value

:save value must boolean. before it was string.
json-read/load cleanup
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
Merge remote-tracking branch 'origin/develop' into feature/autoprofile

Conflicts:
	README.md
	wandbox.el