add missing testcase to day 9
awful day 9 solution bleh
flamegraph.svg snuck in there!
day 7 optimizations

- no need to sort thanks to `select_nth_unstable()`
- don't copy the array around
small tweak (convers sum() to fold())
cleanup some clippy warnings
move to include_str!() macro for all data

Move away from I/O to just including the data in the program via macro.
day 4 logic simplification
day 3 and 4 solutions