Update sdk core to 9.1.0 (#7)

Author: emlaver

pom.xml

@@ -15,7 +15,7 @@
     <packaging>pom</packaging>
 
     <properties>
-        <sdk-core-version>9.0.1</sdk-core-version>
+        <sdk-core-version>9.1.0</sdk-core-version>
 
         <git-repository-name>cloudant-java-sdk</git-repository-name>