Add Larger RNA for test case (used in bio challenge)

In t/translate_rna.t
  Added subtest:
    Test file_to_protein method with valid, Large RNA string
  This uses a large RNA string from rosalind and a large protein result
  file to compare to

Added the follow files for the above subtest:
  t/big_protein_result.txt
  t/big_rna_string.txt