Add dev requires.

setup.py

@@ -17,6 +17,13 @@ setup(
         'passlib>=1.7.1',
         'arrow>=0.10.0',
     ],
+    extras_require={
+        'dev': [
+            'ipython',
+            'ipdb',
+            'flask-shell-ipython',
+        ],
+    },
     setup_requires=[
         'pytest-runner',
     ],