Log Message:
Update ruby-parser to 3.9.0.

=== 3.9.0 / 2017-04-13

* 1 major enhancement:

  * Added tentative ruby 2.4 support. Probably missing things.

* 13 minor enhancements:

  * Added RubyParser.latest.
  * Added RubyParser::Parser.version to make version range comparisons easier
  * Changed superclasses of all parsers to RubyParser::Parser
  * Cleaned up a lot of the version specific code to be more generic/flexible.
  * Documented how to add new versions in README.
  * Moved RubyParser from ruby_parser_extras.rb into ruby_parser.rb to fix \ 
bootstrap issues.
  * Renamed RubyParserStuff#get_match_node to new_match. Aliased and deprecated.
  * Renamed RubyParserStuff#logop to logical_op. Aliased and deprecated.
  * Renamed RubyParserStuff#node_assign to new_assign. Aliased and deprecated.
  * Renamed all parsers to RubyParser::V##.
  * Revamped grammar preprocessing to make adding new versions easier.
  * RubyParser.for_current_ruby falls back to latest if current not available.
  * Subclasses of RubyParser::Parser register themselves into RubyParser::VERSIONS.

* 4 bug fixes:

  * Fixed `&.` after newline. (presidentbeef)
  * Fixed bug setting line number for hash literals to line of opening brace.
  * Fixed grammar preprocessing bug.
  * Properly handle kDO with no-parens stabby lambda. (presidentbeef)