Added description for problem 4.

Signed-off-by: Andrew Coomes <ajc@ajcdrift.com>
Added palindrome check subroutine.

Signed-off-by: Andrew Coomes <ajc@ajcdrift.com>
Added solution to problem 4. Removed
palindrome checker in favor of Perl's
reverse function.

Signed-off-by: Andrew Coomes <ajc@ajcdrift.com>