replace Open3.popen3 with Open3.capture3
replace Open3.popen3 with Open3.capture3

* popen3 gets stuck on full buffer
* @see https://stackoverflow.com/questions/8952043/how-to-fix-hanging-popen3-in-ruby

jeremyf/dragonfly,jeremyf/dragonfly,markevans/dragonfly,markevans/dragonfly