update readme
fix flatter image
reorganize files
reorganize 206
start problem 11
add coinbase button; fix travis button; remove flattr
tidy up code
go back to old layout
restart problem 11
implement adjacents_down

takes vertical adjacent elements in matrix from specified index in a downwards direction.
finish ability to collect adjacent groups
complete right and down products
fix diagonal right
fix adjacents right to grap correct results
fix diagonal left and solve smaller matrix
solve problem 11 (not proud of the code, a little rusty ;D)
start on problem 15
refactor problem 4
refactor first three problems
ensure problem 3 solves within minute