CHANGELOG.md in benchmark_driver-0.15.5 vs CHANGELOG.md in benchmark_driver-0.15.6

@@ -1,4 +1,8 @@
+# v0.15.6
+
+- Fix new keyword argument warnings for the latest Ruby 2.7
+
 # v0.15.5
 
 - Propagate `RUBYOPT` to a runner process when executables are not specified
   - This effectively propagates `bundle exec` to child processes
 - Fix unused variable warning in `benchmark_driver/ridkuse.rb`