Update README
Update README

Update reference to method signature from `sharedClientWithProjectId` to
`sharedClientWithProjectID`, update KIOEventStore to KIODBStore in
README, and remove unnecessary NSString stringWithFormat from NSLog code
snippet

heitortsergent/KeenClient-iOS,keenlabs/KeenClient-iOS,keenlabs/KeenClient-iOS,keenlabs/KeenClient-iOS,heitortsergent/KeenClient-iOS,heitortsergent/KeenClient-iOS,heitortsergent/KeenClient-iOS,heitortsergent/KeenClient-iOS