add flush_at_shutdown option to buf_memory
Merge pull request #286 from sonots/flush_at_shutdown

add flush_at_shutdown option to buf_memory
Relax http_parser.rb gem version for version 0.6.x
Merge pull request #288 from fluent/relax-http_parser.rb-version

Relax http_parser.rb gem version for version 0.6.x