added npm badge; added change log;  removed API reference
added npm badge; added change log;  removed API reference

ibm-bluemix-mobile-services/bms-clientsdk-cordova-plugin-core,ibm-bluemix-mobile-services/bms-clientsdk-cordova-plugin-core,ibm-bluemix-mobile-services/bms-clientsdk-cordova-plugin-core