Add comment about proxy env pass through

For users in a proxy environment, checking the doc urls requires being
able to pass through the proxy environment variables. Include a simple
comment along with the tox command requiring it to help users checking
any links added are valid.

Add some references to documentation, both in the detailed
documentation and the quick README.rst that would be more commonly
checked.

Change-Id: I2316bc1b7e845c29a8b248eef4668a6099d109f7

README.rst

@@ -69,6 +69,21 @@ This consistency will help users avoid simple mistakes when writing
 YAML, as well as developers when matching YAML components to Python
 implementation.
 
+Unit Tests
+----------
+
+Unit tests have been included and are in the ``tests`` folder. Many unit
+tests samples are included as examples in our documentation to ensure that
+examples are kept current with existing behaviour. To run the unit tests,
+execute the command::
+
+    tox -e py34,py27
+
+* Note: View ``tox.ini`` to run tests on other versions of Python,
+  generating the documentation and additionally for any special notes
+  on running the test to validate documentation external URLs from behind
+  proxies.
+
 Installing without setup.py
 ---------------------------
 

doc/source/installation.rst

@@ -33,6 +33,15 @@ locally execute the command::
 The generated documentation is then available under
 ``doc/build/html/index.html``.
 
+As over time URLs change or become stale there is also a testenv available
+to verify any links added. To run locally execute the command::
+
+    tox -e docs-linkcheck
+
+* Note: When behind a proxy it is necessary to use ``TOX_TESTENV_PASSENV``
+  to pass any proxy settings for this test to be able to check links are
+  valid.
+
 Unit Tests
 ----------
 

tox.ini

@@ -39,6 +39,9 @@ commands = jenkins-jobs test -o .test/new/out/ .test/new/config/
 commands = python setup.py build_sphinx {posargs}
 
 [testenv:docs-linkcheck]
+# If you are behind a proxy, for this test to work you will need to set
+# TOX_TESTENV_PASSENV="http_proxy https_proxy no_proxy ..." to pass
+# through the proxy environment settings to be able to validate any urls.
 commands = python setup.py build_sphinx -b linkcheck
 
 [testenv:venv]