Add unit test to assert `gt fingerprint` is case insensitive.

Data used in this unit test:
- U89959_ests_gi_8690080_soft_masked.fas is gi|8690080 from U89959_ests.fas,
  but arbitrarily soft-masked.
- U89959_ests_gi_8690080_unmasked.checklist is MD5 fingerprint of gi|8690080
  from U89959_ests.fas.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>