HitChat request timeout setting

see https://github.com/czarneckid/hipchat-api/blob/master/lib/hipchat-api.rb#L9
Merge branch 'feature/hipchat_timeout' of github.com:matsumana/fluent-plugin-hipchat into matsumana-feature/hipchat_timeout

Conflicts:
	README.rdoc
	lib/fluent/plugin/out_hipchat.rb