Use internal ut8_convert to transliterate unknown $_SERVER chars to ASCII
Request data to UTF-8; encode into JSON correctly

Valid UTF-8 chars in $_SERVER are set to that encoding then encoded
correctly into json. This is achieved by the a new wrapper function that
removes escaped unicode characters (\u00ce), as json_encode only
includes this functionality from PHP 5.4.

Invalid UTF-8 codepoints in form data and raw data are ignored as
before, valid ones will be correctly encoded.

+ minor refactor to bring API endpoint to top of class
Update docs
Merge pull request #36 from MindscapeHQ/requestdata_to_utf8_json

Requestdata to utf8 json