Rewritten in Kotlin

[Mygod]

Fix #26.

DO NOT MERGE UNTIL THESE ARE FIXED:

• [x] https://github.com/shadowsocks/kcptun/pull/8 and update reference;
• [ ] Plugin library 0.1.1;
• [ ] Travis build;
• [ ] Double SIGTERM glitch.

[Mygod]

By the way I'm surprised that nobody has done this.

@madeye Also do you think you'll be able to rewrite simple-obfs-android in Kotlin as well? That one should be as simple as this one.