add drone.io configuration file (see http://readme.drone.io/usage/overview/ )

9a964b06 · Yushin Washio · c5e07c7b · 9a964b06
Commit 9a964b06 authored Apr 15, 2016 by Yushin Washio
--- a/.drone.yml
+++ b/.drone.yml
+build:
+  image: gcc
+  commands:
+    - make