Fix misspelling in the "README.rst"

Change the description to
1."- Tempest should be self-testing."
2."The etc/tempest.conf.sample attempts to be a
 self-documenting version of the configuration."
3."However, because large parts of Tempest
  are self-verifying there might be uncaught
  issues running on Python 3.4"

Closes-Bug: #1486904

Change-Id: Ic5a5446f62a3bfa7befb5ca9acbb577446faaba4
diff --git a/README.rst b/README.rst
index 431be7c..7a7dfa6 100644
--- a/README.rst
+++ b/README.rst
@@ -32,7 +32,7 @@
   parts as load generation for an OpenStack cloud.
 - Tempest should attempt to clean up after itself, whenever possible
   we should tear down resources when done.
-- Tempest should be self testing.
+- Tempest should be self-testing.
 
 Quickstart
 ----------
@@ -94,7 +94,7 @@
 
 Detailed configuration of Tempest is beyond the scope of this
 document see :ref:`tempest-configuration` for more details on configuring
-Tempest. The etc/tempest.conf.sample attempts to be a self documenting version
+Tempest. The etc/tempest.conf.sample attempts to be a self-documenting version
 of the configuration.
 
 You can generate a new sample tempest.conf file, run the following
@@ -142,7 +142,7 @@
 support running with Python 3.4. A gating unit test job was added to also run
 Tempest's unit tests under Python 3.4. This means that the Tempest code at
 least imports under Python 3.4 and things that have unit test coverage will
-work on Python 3.4. However, because large parts of Tempest are self verifying
+work on Python 3.4. However, because large parts of Tempest are self-verifying
 there might be uncaught issues running on Python 3.4. So until there is a gating
 job which does a full Tempest run using Python 3.4 there isn't any guarantee
 that running Tempest under Python 3.4 is bug free.