Upgrade to jclouds 2.2.0

Release notes:

https://jclouds.apache.org/releasenotes/2.2.0/

Notably this works around the ancient gson dependency.  Fixes #148.

pom.xml

@@ -308,7 +308,7 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <java.version>1.7</java.version>
-    <jclouds.version>2.1.2</jclouds.version>
+    <jclouds.version>2.2.0</jclouds.version>
     <slf4j.version>1.7.28</slf4j.version>
     <shade.prefix>${project.groupId}.shaded</shade.prefix>
     <surefire.version>2.20</surefire.version>