Argcomplete as an optional requirement.

setup.py

@@ -20,9 +20,11 @@ setup(
     scripts      = ['pubs/pubs'],
 
     install_requires = ['pyyaml', 'bibtexparser', 'python-dateutil', 'requests',
-                        'configobj', 'argcomplete',
+                        'configobj',
                         'beautifulsoup4'], # to be made optional?
     tests_require = ['pyfakefs>=2.7'],
+    extra_require = {'autocompletion': ['argcomplete'],
+                     },
 
     classifiers=[
         'Development Status :: 4 - Beta',