Python 3 compatibility

[garciaargos]

Nice script, thanks a lot. I just received a brand new RD200 and the compatibility with Python 3 can be fixed by changing line 49:

RadonEyeWrite.write(bytes("\x50"))

with:

RadonEyeWrite.write(bytes("\x50", "ascii"))

Unfortunately this wouldn't work with 2.7. But 2.7 has been End of Life for 2 years :-)