Bio.Alphabet: Add ProteinAlphabet

Signed-off-by: Kai Blin <kai.blin@biotech.uni-tuebingen.de>
Bio.Alphabet tests: Unify and clarify test names

Signed-off-by: Kai Blin <kai.blin@biotech.uni-tuebingen.de>
Bio.Alphabet tests: Use === to compare with null

Signed-off-by: Kai Blin <kai.blin@biotech.uni-tuebingen.de>
Add Travis CI setup

Signed-off-by: Kai Blin <kai.blin@biotech.uni-tuebingen.de>