Update version string to 1.4.0 (#512)

Author: amudukutore

docs/conf.py

@@ -83,7 +83,7 @@
     # The short X.Y version.
     version = u'v{}.{}'.format(v[0], v[1])
     # The full version, including alpha/beta/rc tags.
-    release = u'v{}.{}.{}-dev'.format(v[0], v[1], v[2])
+    release = u'v{}.{}.{}'.format(v[0], v[1], v[2])
 
 # def setup(app):
 #    app.add_config_value('versionlevel', '', 'env')