[maven-release-plugin] prepare release v2.1.1
[maven-release-plugin] prepare release v2.1.1

segeon/metrics-spring,ryantenney/metrics-spring,jxqlovejava/metrics-spring,alex859/metrics-spring,davidkarlsen/metrics-spring,wyzssw/metrics-spring,karl82/metrics-spring,fgaule/metrics-spring,jongyoul/metrics-spring