Bump beta version to 1.0.0b4

I seem to have lost the commit that bumped the version to
1.0.0b3 when my crostini container went away.

Author: ento

setup.py

@@ -7,7 +7,7 @@
 
 setup(
     name='elm-doc',
-    version='1.0.0b2',
+    version='1.0.0b4',
     url='https://github.com/ento/elm-doc',
     license='BSD 3-clause',
     author='Marica Odagaki',