Hand URDF: Add mimic tag, adjust joint limits

CHANGELOG.md

 # CHANGELOG
 
+## 0.4.0 - UNRELEASED
+
+  * Added `mimic` tag for gripper fingers to URDF
+
 ## 0.3.0 - 2018-02-22
 
 Requires `libfranka` >= 0.3.0

franka_description/robots/hand.xacro

@@ -51,14 +51,15 @@
       <child link="${ns}_leftfinger"/>
       <origin xyz="0 0 0.0584" rpy="0 0 0"/>
       <axis xyz="0 1 0"/>
-      <limit effort="20" lower="-0.001" upper="0.04" velocity="0.3"/>
+      <limit effort="20" lower="0.0" upper="0.04" velocity="0.3"/>
     </joint>
     <joint name="${ns}_finger_joint2" type="prismatic">
       <parent link="${ns}_hand"/>
       <child link="${ns}_rightfinger"/>
       <origin xyz="0 0 0.0584" rpy="0 0 0"/>
       <axis xyz="0 -1 0"/>
-      <limit effort="20" lower="-0.001" upper="0.04" velocity="0.3"/>
+      <limit effort="20" lower="0.0" upper="0.04" velocity="0.3"/>
+      <mimic joint="${ns}_finger_joint1" />
     </joint>
   </xacro:macro>
 </robot>