Pre-release 2.1-0

** Changes **

• a better looking GUI by @Maneetbal: #49
• allow for switching to different page styles
• implemented experimental Web Socket transport: only works in a Secure Context and with H264: #39
• don't fail when the host doesn't have a MAC address: #47
• fixed a bug where the sidebar couldn't be clicked when the stats were overpopulated: #46
• added the option to set and force a specific codec: #45
• implemented support for mouse button 4,5: #41