Day 37 Part 6 - Complete P99

Verified 2 more test cases given, thereby completing P99, and
all 99 Scala problems =)

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>
Day 37 Part 7 - Update README.txt

Signed-off-by: Pang Yan Han <pangyanhan@gmail.com>