Revert "JSON_PRETTY_PRINT and remove @ operator"

This reverts commit 7b4072aca7e4e5e365277910d2baac8a581ec5bf.
remove @ operator from json_encode
Guzzle\uri_template to Rize\UriTemplate

pecl/uri_template is preferable.
update composer.json
update README for 5.5
add function comment