Bump version in git to 10.0.0.dev0

It is confusing to have different versions of the code self-identify
with the same version number.  In my experience it's always best to
increment the version number and add a .dev0 suffix right after making a
release.  When it's time to make a new release, you remove the .dev0,
commit, tag that commit, then make second commit that bumps the version
and adds .dev0 back.

This way only releases identify themselves as "version X.Y.Z" with no
.dev0 suffix and it's immediatelly apparent when you've got a prerelease
installed from git.

setup.py

@@ -47,7 +47,7 @@ from distutils.core import Distribution
 from distutils.command.build import build
 
 # the application version
-AppVersion = "9.4.0"
+AppVersion = "10.0.0.dev0"
 # the application name
 AppName = "LinkChecker"
 Description = "check links in web documents or full websites"