docs(README): add OUR SUPPORT POLICY section

twada · twada · commit 6e3f981489c2 · 2016-12-30T11:14:41.000+09:00
diff --git a/README.md b/README.md
@@ -87,6 +87,16 @@ $ cat /path/to/src/target.js | unassert > /path/to/build/target.js
 ```
 
 
+OUR SUPPORT POLICY
+---------------------------------------
+
+We support Node under maintenance. In other words, we stop supporting old Node version when [their maintenance ends](https://github.com/nodejs/LTS).
+
+This means that any other environment is not supported.
+
+NOTE: If unassert-cli works in any of the unsupported environments, it is purely coincidental and has no bearing on future compatibility. Use at your own risk.
+
+
 AUTHOR
 ---------------------------------------
 * [Takuto Wada](https://github.com/twada)
