Release 1.2.2

Produce a Pure Python Wheel instead of a source distribution for Linux.
This speeds up installation and simplifies distribution building.

	* setup.py: Drop support for sdist; add support for bdist_wheel
    without --plat-name switch; persist README.rst; increment version
	* dtls/__init__.py: Increment version

dtls/__init__.py

@@ -32,7 +32,7 @@ sockets.
 wrap_socket's parameters and their semantics have been maintained.
 """
 
-VERSION = 1, 2, 0
+VERSION = 1, 2, 2
 
 def _prep_bins():
     """