corrected minimum grid size error message text

Update README.md

fixed some bugs, made variables for initial values to refer to

removed console.log instance

fixed bug in checking if users has clicked cancel on setting grid size

don't pop up message if user cancels grid creation

moved all buttons next to each other

made shading mode shade quicker

Added flex layout and basic styling

Removed logging lines

fixed shader function

Added classic (black colour) mode

added TODO for shader bug fix

Add eraser

refactoring