Fix to rxbuf reader

[TheCedarPrince]

Per #19 and the suggestion from @Alexander-Barth, I was able to make this fix to PiGPIO.jl! It works like it does in the python implementation now. I did have to do one more fix which was to explicitly pass in Base.read. Otherwise, this was what Alexander had suggested. :)

Thanks!

[Alexander-Barth]

Thank a lot for the PR! Can you also check that it also work without the Base. prefix for the read function ? I know that in multiple places we have the Base prefix, but I am not sure what was the reason for this. If you get an error, can you paste the error message here?

[TheCedarPrince]

Sure! Here is the error that I get without Base.read:

ERROR: MethodError: no method matching read(::Sockets.TCPSocket, ::Int32)
You may have intended to import Base.read

Closest candidates are:
  read(::Pi, ::Any)
   @ PiGPIO ~/PiGPIO.jl/src/pi.jl:442

Stacktrace:
 [1] rxbuf(self::Pi, count::Int32)
   @ PiGPIO ~/PiGPIO.jl/src/pi.jl:354
 [2] spi_xfer(self::Pi, handle::Int32, data::Vector{UInt8})
   @ PiGPIO ~/PiGPIO.jl/src/spiSerial.jl:205
 [3] top-level scope
   @ REPL[5]:1

This goes away when I use Base.read. Not entirely sure why -- any thoughts @Alexander-Barth ?