Merge pull request #2 from arialdomartini/intro

README references the book we are studying
Merge pull request #3 from RobMcZag/master

Added first test and developed GenerateQRCode to pass it.
Red - Added test checking we create a good PNG image.
Green - Implemented image generation in GenerateQRCode
Refactor - Refactored main and GenerateQRCode to remove buffers and byte
slices.
Refactor - Fixed test broken from code refactring