fixed seesaw documentation and added readme

worlds/icub_seesaw_world/README.md

@@ -0,0 +1,15 @@
+## To load iCub seesaw world in Gazebo
+
+Normally, for loading a `world`, Gazebo needs to be launched in the folder where the `world` is. You can avoid this by appending these lines to your `.bashrc`:
+
+```
+source /usr/share/gazebo/setup.sh
+export GAZEBO_RESOURCE_PATH=$GAZEBO_RESOURCE_PATH:/PATH/WHERE/YOUR/WORLD/IS
+
+```
+
+Furthermore, if you are working with Simulink controllers, it is necessary to sincronize Gazebo with Simulink by running Gazebo with the option `-slibgazebo_yarp_clock.so`. 
+
+Final command to run in the terminal is something like this: `gazebo -slibgazebo_yarp_clock.so nameOfYourWorld`. For seesaw demo, it is also required to start Gazebo in "pause" mode, and therefore final command will be: `gazebo -slibgazebo_yarp_clock.so icub_seesaw_world -u`.
+
+

worlds/icub_seesaw_world/icub_seesaw_world

@@ -12,14 +12,15 @@
       <uri>model://ground_plane</uri>
     </include>
 
-    <!-- Chair for sittin' on -->
+    <!-- Seesaw -->
     <include>
         <uri>model://seesaw</uri>
     </include>
 
-    <!-- iCub in the sitting position -->
+    <!-- iCub above the seesaw -->
     <include>
     <uri>model://icub_on_seesaw</uri>
     </include>
+
   </world>
 </sdf>