Deploy to bintray

please set to project properties.

* `$bintrayUser`: user name
* `$bintrayKey `: api key

if you want to get api key, please see https://bintray.com/profile/edit

please run `$ gradle clean bintrayUpload`.

ref. https://github.com/bintray/gradle-bintray-plugin
ref. https://github.com/srs/gradle-node-plugin/blob/master/build.gradle