Added os.system(…).
Now returning exit code from os.system(…) call.
Added os.popen2+os.popen3.
All extensions are now explicitly public.
Added .write(s).
open(…)-modes "w" and "a" now working as expected.
Added shutil.copyfile(…).
Added tests for: open(…) [modes: w, a, r (default)] + fh.write + fh.close + os.path.exists.
merged upstream changes