updated guava version

Author: fehguy

modules/swagger-core/pom.xml

@@ -104,7 +104,7 @@
     <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
-      <version>12.0</version>
+      <version>18.0</version>
       <scope>test</scope>
     </dependency>
     <dependency>