test => diff with empty array
test => diff with same array
test => diff
Merge branch 'array_diff' into master
add test into all-tests.html
test => return [] if n == -1
test => return [fib(0)..fib(n)] if n >= 0
fix bug=> return size
refactoring => best practice from codewars
Merge branch 'complete_fibonacci_series' into master