doc: Add PyPi information to README.md

 - Added PyPi installation info
 - Added source code download/cloning info
 - Updated development status in setup.py

Signed-off-by: Tim Hall <tim.hall@arm.com>
Change-Id: I5c2f7dfe19a222f008b5f825c58d0fec14792bc1
diff --git a/setup.py b/setup.py
index 8d88997..1ef462a 100644
--- a/setup.py
+++ b/setup.py
@@ -41,7 +41,7 @@
     author="Arm Ltd.",
     license="Apache License 2.0",
     classifiers=[
-        "Development Status :: 4 - Beta",
+        "Development Status :: 5 - Production/Stable",
         "Intended Audience :: Developers",
         "License :: OSI Approved :: Apache Software License",
         "Operating System :: POSIX :: Linux",