Upstream a number of changes to git.

Changes:
- Updates to README / os_setup for common installation issues
  by ebrevdo, vrv, wicke, anelia, dga

- Add a test for backwards compatibility checks by Josh

- Simplifications to tiling/padding of scalars by bsteiner

- Improve listing of devices when no devices are known by Matthieu

Base CL: 107607137
diff --git a/README.md b/README.md
index 1a53403..c581442 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,9 @@
 
 ## Binary Installation
 
-The TensorFlow Python API requires Python 2.7.
+The TensorFlow Python API currently requires Python 2.7: we are
+[working](https://github.com/tensorflow/tensorflow/issues/1) on adding support
+for Python 3.0.
 
 The simplest way to install TensorFlow is using
 [pip](https://pypi.python.org/pypi/pip) for both Linux and Mac.
@@ -40,7 +42,7 @@
 more detailed installation instructions, see
 [here](tensorflow/g3doc/get_started/os_setup.md#detailed_install).
 
-### Ubuntu/Linux
+### Ubuntu/Linux 64-bit
 
 ```bash
 # For CPU-only version