Added the initial version of the README file.

README.md

+# Description
+
+This ROS package contains physical descriptions of the Ana robot build
+at IRI. The following files are provided:
+
+ * Xacro macro with all the sensors available on the robot.
+
+ * Main xacro file to be used to import the robot.
+
+# Dependencies
+
+This node has the following dependencies:
+
+ * [iri_pioneer3_description](https://gitlab.iri.upc.edu/labrobotica/ros/platforms/pioneer3/iri_pioneer3_description)
+
+ * [iri_bno055_imu_description](https://gitlab.iri.upc.edu/labrobotica/ros/sensors/imu/iri_bno055_imu_description)
+
+ * [iri_velodyne_lidar_description](https://gitlab.iri.upc.edu/labrobotica/ros/sensors/ranger3d/iri_velodyne_lidar_description)
+
+Additionally, for simulation the following dependencies are also required:
+
+ * [iri_sked_steering_gazebo](https://gitlab.iri.upc.edu/labrobotica/ros/platforms/iri_skid_steering_gazebo)
+
+ * [iri_imu_gazebo](https://gitlab.iri.upc.edu/labrobotica/ros/sensors/imu/iri_imu_gazebo)
+
+ * [iri_velodyne_gazebo](https://gitlab.iri.upc.edu/labrobotica/ros/sensors/ranger3d/iri_velodyne_gazebo)
+
+# Install
+
+This package, as well as all IRI dependencies, can be installed by cloning the
+repository inside the active workspace:
+
+```
+roscd
+cd ../src
+git clone https://gitlab.iri.upc.edu/labrobotica/ros/platforms/pioneer3/iri_pioneer3_description.git 
+```
+
+However, this package is normally used as part of a wider installation (i.e. a
+robot, an experiment or a demosntration) which will normally include a complete
+rosinstall file to be used with the [wstool](http://wiki.ros.org/wstool) tool.
+
+# How to use it
+
+The *ana.xacro* file can be used to import the robot description for the real 
+robot and to spawn it in simulation.
+
+The main xacro macro has the following parameters:
+
+ * **name:** (default: ana) name of the robot in case there ara several instances.
+