Fixed install via setup.py on Python 2.7, 3.4, 3.5
Fixed install via setup.py on Python 2.7, 3.4, 3.5

Details:

* The decorator package 5.0 dropped support for Python 2.7 and 3.4. Since
  setup.py does not check supported Python versions of dependent packages,
  it attempts to install decorator 5.0.4 on python 2.7 which fails.
  This fix pins the version of decorator to below 5.0 on py27 and py34.

* Checking the other packages in requirements.txt reveals that the versions of
  the requests and stomp.py packages also should be pinned on py27, py34 and
  py35, just to be on the safe side, even though no install issue is known.

Signed-off-by: Andreas Maier <38dbb04957d222ea6ce72de72413b1e55e665472@de.ibm.com>

zhmcclient/python-zhmcclient,zhmcclient/python-zhmcclient