update readme

[missxa]

• - ROS bridge is not required for you
• - In a new terminal go to /roboy_snapchat_filter/scripts/ directory and execute rosrun roboy_snapchat_filter snapchat_server.py <- requiring a user to navigate to a specific directory is not ideal. technically you can execute rosrun of your script from anywhere, but because you are dependent on relative paths in your script this is not possible. please change to global paths in your code and it will solve the problem
• - speech_synthesis launch file? why is it there?
• - add pictures of the filters that are possible
• - add exact syntax of a ROS service call to trigger a filter
• - mention it is a rospackage and depends on roboy_communication_cogntion

[sebo361]

All fixed :)