Update release notes.

Author: monkpow

README.md

@@ -560,6 +560,7 @@ app.use('/', proxy('internalhost.example.com', {
 
 | Release | Notes |
 | --- | --- |
+| 1.6.0 | Do gzip and gunzip aysyncronously.   Test and documentation improvements, dependency updates. |
 | 1.5.1 | Fixes bug in stringifying debug messages. |
 | 1.5.0 | Fixes bug in `filter` signature.  Fix bug in skipToNextHandler, add expressHttpProxy value to user res when skipped.  Add tests for host as ip address. |
 | 1.4.0 | DEPRECATED. Critical bug in the `filter` api.|