Add more unit tests for `PhutilJSONParser`.

Summary: Added some additional unit tests taken from the [[https://github.com/Seldaek/jsonlint | original source]].

Test Plan: Ran `arc unit`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9638