fix build with wheel

- add pyproject.toml to MANIFEST.in
- bump version in setup.py

MANIFEST.in

 recursive-include DTLSSocket/tinydtls *.h LICENSE ABOUT.md configure.ac CONTRIBUTING.md README Makefile.in doc/Doxyfile.in
-include DTLSSocket/dtls.pyx DTLSSocket/tdtls.pxd LICENSE
+include DTLSSocket/dtls.pyx DTLSSocket/tdtls.pxd LICENSE pyproject.toml

setup.py

@@ -26,7 +26,7 @@ with open("README.md", "r") as fh:
 
 setup(
     name="DTLSSocket",
-    version='0.1.11a2',
+    version='0.1.11',
     description = "DTLSSocket is a cython wrapper for tinydtls with a Socket like interface",
     long_description=long_description,
     long_description_content_type="text/markdown",