Example Python file and README Update

[Walt-H]

Hi hanyazou,

I am a very big fan of your work, and I am very thankful for your Python Tello client :D !!

With a lot of people having questions about mplayer and video_and_keyboard.py, I wanted to contribute solutions that have helped me and others who have reported similar issues.

First, with people typically using video_and_keyboard.py first, I made the example code platform independent for when users want to save an image or video.

Lastly, since all video examples assume mplayer is installed, I added sections to help users install it based on each major platform.

Hope all is well during this time!

Best, Walt

[Helge543]

sry but I tried your "made_keyboard_and_video.py platform neutral" version for Ubuntu 18.04 incl. your advices from readme.txt (installing the player) but it did not work. still black screen with battery status etc. on the upper left. do you have any tipps for me?

[Gardenia-Ho]

sry but I tried your "made_keyboard_and_video.py platform neutral" version for Ubuntu 18.04 incl. your advices from readme.txt (installing the player) but it did not work. still black screen with battery status etc. on the upper left. do you have any tipps for me?

Hi, I have the same problem on Windows10. Have you solved it?