CodonTable.pm: Fix for issue #90. Added new codon tables 24 & 25 and
moved special 'Strict' table to ID 0, so it don't interfere with
new tables in the future. Deleted a dead link and updated other
tables according to the latest definitions. Since ID 0 now exists
and is used by 'Strict', the 'id' subroutine now returns 1
(standard table) for invalid specified ids (besides the warning).
Also fixed some indentations.
CodonTable.t: Added tests to cover all the changes plus a few extras
to improve code coverage after looking Coveralls report.