Temporary fix on Python doc to alleviate confusion

cc grpc/grpc-common#274, #2896

src/python/README.md

@@ -52,9 +52,19 @@ BUILDING FROM SOURCE
 ---------------------
 - Clone this repository
 
+- Initialize the git submodules
+```
+$ git submodule update --init
+```
+
+- Make the libraries
+```
+$ make
+```
+
 - Use build_python.sh to build the Python code and install it into a virtual environment
 ```
-$ tools/run_tests/build_python.sh
+$ CONFIG=opt tools/run_tests/build_python.sh 2.7
 ```
 
 TESTING
@@ -62,7 +72,7 @@ TESTING
 
 - Use run_python.sh to run gRPC as it was installed into the virtual environment
 ```
-$ tools/run_tests/run_python.sh
+$ CONFIG=opt PYVER=2.7 tools/run_tests/run_python.sh
 ```
 
 PACKAGING