Rewrite API, fix a few edge cases, add support for PHP 7.0, 7.1, and 7.2, as well as AST Version 45
The API now exposes instance methods instead of static methods.
Calls to change options on one converter instance should no longer affect other converter instances
AST version 40, 45, and 50 are now supported.
Fix bugs found in 0.0.2, add test cases.