Remove tox 2.1.1 requirement in README.md

In order to support new tox syntax used in tox.ini, it is required to
use tox version 2.3.1 or greater.

Resolves openbmc/openbmc-test-automation#73

Change-Id: I36e2e891ccd93e795cd29310ed042522e0b68754
Signed-off-by: Jay Azurin <jmazurin@us.ibm.com>
diff --git a/README.md b/README.md
index 0032eec..956b9b7 100755
--- a/README.md
+++ b/README.md
@@ -4,11 +4,12 @@
 ----------

 

 To run openbmc-automation first you need to install the prerequisite python

-packages which will help to invoke tests through tox.

+packages which will help to invoke tests through tox.  Note that tox

+version 2.3.1 or greater is required.

 

 Install the python dependencies for tox

 ```shell

-    $ easy_install tox==2.1.1

+    $ easy_install tox

     $ easy_install pip

 ```