Bumped version due to updated dev-dependency

in Pipfile.lock, this version doesn't change any behaviour for users of
the library nor any functionallity, this is only for library developers
to have updated lock-dependencies.

This is due to the old lock file containing a dev dependency with a version of
twine which is connected to requests 2.19.1 which had a moderate security issue
published earlier today

setup.py

@@ -20,7 +20,7 @@
     description="A markdown renderer focusing on security first",
     long_description=long_description,
     long_description_content_type="text/markdown",
-    version="18.10.2",
+    version="18.10.3",
     py_modules=["app"],
     packages=find_packages(exclude=["tests"]),
     install_requires=["cmarkgfm", "bleach"],