update changelog for v1.7.0 (#356)

Author: jbardin

CHANGELOG.md

@@ -4,6 +4,9 @@ CHANGES:
 
 * When go-plugin encounters a stack trace on the server stderr stream, it now raises output to a log-level of Error instead of Debug. [[GH-292](https://github.com/hashicorp/go-plugin/pull/292)]
 
+ENHANCEMENTS:
+
+* Don't spend resources parsing log lines when logging is disabled [[GH-352](https://github.com/hashicorp/go-plugin/pull/352)]
 
 ## v1.6.2