bindings --> api; and moved nlsat/sat/subpaving tactics

src/api/python/README.txt

@@ -0,0 +1,20 @@
+You can learn more about Z3Py at:
+http://rise4fun.com/Z3Py/tutorial/guide
+
+On Windows, you must build Z3 before using Z3Py.
+To build Z3, you should executed the following command
+in the Z3 root directory at the Visual Studio Command Prompt
+
+       msbuild /p:configuration=external
+
+If you are using a 64-bit Python interpreter, you should use
+
+       msbuild /p:configuration=external /p:platform=x64
+
+
+On Linux and OSX, you must install Z3Py, before trying example.py.
+To install Z3Py on Linux and OSX, you should execute the following 
+command in the Z3 root directory
+
+        sudo make install-z3py
+