fix(MarkerClusterer): typo method name of getAverageCenter
fix(MarkerClusterer): typo method name of getAverageCenter

* Original commit: eec79454e7e28873e4631ed8fc0a114b94ecfafd
* Closes #203
* Closes #204

jossi87/react-google-maps,joshcarr/react-google-maps,RishabhJain96/react-google-maps,RishabhJain96/react-google-maps,jossi87/react-google-maps,tomchentw/react-google-maps