Add new dev version to switcher (#289)

Author: stefmolin

docs/_static/switcher.json

@@ -4,6 +4,11 @@
         "version": "stable",
         "url": "https://stefaniemolin.com/data-morph/stable/"
     },
+    {
+        "name": "0.4 (dev)",
+        "version": "dev",
+        "url": "https://stefaniemolin.com/data-morph/dev/"
+    },
     {
         "name": "0.2",
         "version": "0.2",

src/data_morph/__init__.py

@@ -28,5 +28,5 @@
 and `this slide deck <https://stefaniemolin.com/data-morph-talk/#/>`_.
 """
 
-__version__ = '0.3.0'
+__version__ = '0.4.0.dev0'
 MAIN_DIR = __name__