Fix diff drive plugin because of deprecation of legacyMode (#17)

Author: eborghi10

ca_description/urdf/create_base_gazebo.urdf.xacro

@@ -20,7 +20,7 @@
         <publishWheelTF>true</publishWheelTF>
         <publishOdomTF>true</publishOdomTF>
         <publishWheelJointState>true</publishWheelJointState>
-        <legacyMode>true</legacyMode>
+        <legacyMode>false</legacyMode>
         <odometrySource>world</odometrySource>
         <publishTf>1</publishTf>
       </plugin>

ca_description/urdf/create_wheel.xacro

@@ -34,7 +34,7 @@
     <origin xyz="${x} ${y} ${z}" rpy="0 0 0" />
     <parent link="base_link" />
     <child link="${prefix}_wheel_link" />
-    <axis xyz="0 1 0" />
+    <axis xyz="0 -1 0" />
   </joint>
 </xacro:macro>