Added the README file.

README.md

+# Description
+
+This package is a Gazebo plugin to control the state of a single sempahores in the model car simulator. This package is part of the model car simulator used for the [ADC competition](http://autonomousdrivingchallenge.com/ "ADC competition").
+
+This package in intended to be used with ROS Kinetic under Linux Ubuntu 16.04, although it may work with other ROS versions and Linux variations.
+
+# Dependencies
+
+This node has the following dependencies:
+
+ * gazebo ros 
+
+ * gazebo plugins
+
+All these dependencies can be installed with:
+
+```
+sudo apt-get install ros-kinetic-gazebo-ros ros-kinetic-gazebo-plugins
+```
+
+# How to use it
+
+## Install
+
+This package can be cloned to the active workspace with the following command:
+
+```
+roscd
+cd ../src
+git clone https://gitlab.iri.upc.edu/seat_adc/simulator/color_plugin.git
+```
+
+But it is recommended to follow the [instructions on how to install the model simulator](https://gitlab.iri.upc.edu/seat_adc/simulator/model_car_gazebo).
+
+## running
+
+Each semaphore will provide a service call to change its state. The namespace of the service call depend on the name given to the semaphore. The default model cal simulator provides the following services:
+
+ * /semaphore_intersection1_color_plugin/trigger
+
+ * /semaphore_intersection2_color_plugin/trigger
+ 
+ * /semaphore_intersection3_color_plugin/trigger
+
+ * /semaphore_parking1_color_plugin/trigger
+
+ * /semaphore_parking2_color_plugin/trigger
+
+ * /semaphore_roundabout1_color_plugin/trigger
+
+ * /semaphore_roundabout2_color_plugin/trigger
+
+ * /semaphore_start1_color_plugin/trigger
+
+ * /semaphore_start2_color_plugin/trigger
+
+To change the state of any of these semaphores, call the corresponding service:
+
+```
+rosservice call /semaphore_start1_color_plugin/trigger
+```

package.xml

@@ -50,11 +50,11 @@
   <build_depend>gazebo_plugins</build_depend>
   <run_depend>gazebo_plugins</run_depend>
   
-   <build_depend>message_runtime</build_depend>
-   <run_depend>message_runtime</run_depend> 
+  <build_depend>message_runtime</build_depend>
+  <run_depend>message_runtime</run_depend> 
    
-   <build_depend>message_generation</build_depend>
-   <run_depend>message_generation</run_depend>
+  <build_depend>message_generation</build_depend>
+  <run_depend>message_generation</run_depend>
 
   <build_depend>std_msgs</build_depend>
   <run_depend>std_msgs</run_depend>