refactor: move test_files into tests

test_files/.ipynb_checkpoints/transcript-checkpoint.fasta

tests/test_files/.gitkeep

tests/test_files/Example_GTF_Input.GTF

tests/test_files/cDNA.csv

tests/test_files/cDNA.fasta

tests/test_files/copy_number_file.csv

tests/test_files/copy_number_input.csv

tests/test_files/transcript.fasta

tests/test_files/yeast_example.fa