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
Refactor - Reduce the amount of useless tests.
Merge pull request #4 from RobMcZag/master

Red, Green, Refactor paragraph [p 13-18]