add peptide keyword

setup.py

@@ -16,7 +16,7 @@ metainfo = {
     'license': 'GPLv3',
     'description': 'In silico protein digestion',
     'platforms': ['Linux', 'Unix', 'MacOsX', 'Windows'],
-    "keywords": ["protein", "enzyme", "protease", "digestion"],
+    "keywords": ["protein", "peptide", "enzyme", "protease", "digestion"],
     'classifiers': [
         'Development Status :: 3 - Alpha',
         'Intended Audience :: Science/Research',