Added the initial version of a README file.

README.md

+# Description
+
+This ROS package encapsulates the IMU sensor from the [Hector gazebo plugins package](http://wiki.ros.org/hector_gazebo_plugins) in a xacro macro to simplify its integration. 
+
+# Dependencies
+
+This node has the following ROS dependencies:
+
+  * [Hector gazebo plugins package](http://wiki.ros.org/hector_gazebo_plugins)
+
+This dependencies can be installed with the following command:
+
+```
+sudo apt-get install ros-kinetic-hector-gazebo-plugins
+```
+
+This node has the following ROS IRI dependencies:
+
+  * [IRI Microstrain IMU description](https://gitlab.iri.upc.edu/labrobotica/ros/sensors/imu/iri_microstrain_imu_description).
+
+
+# Install
+
+This package can be cloned to an active workspace with the following command:
+
+```
+roscd
+cd ../src
+git clone https://gitlab.iri.upc.edu/labrobotica/ros/sensors/imu/iri_imu_gazebo.git 
+```
+
+# How to use it
+
+This IMU gazebo model is automatically included when an IMU sensor in included in a xacro or urdf file. This plugin can be fully configured by a YAML file which is provided as a parameter to the xacro macro.
+
+A separate YAML file is provided for each IMU sensor. At the moment the supported sensors are:
+
+ * Microstrain 3dm-gx3-25 
+