3.0.0

There are next changes:

• add support phpunit 7.x and 8.x
• update nikic/php-parser to ^4.3.0, so now version isn't specific
• minimum php version now is 7.0
• now ext-json is required for get nikic/php-parser version for right rewritten files cache
• fixed error 'Unbinding $this of closure is deprecated'