Use the same module name in sample and tests
Use the same module name in sample and tests

The example declares the `dna` module name, but the test uses
`rna_transcript`. This made the `check_exercises.sh` script fail.

exercism/xerlang,NobbZ/xerlang,barberj/xerlang,macintux/xerlang,exercism/xlfe,tmcgilchrist/xerlang,lfex/xlfe