Modify README to allow partial include

Change README to follow similar sections to allow partial inclusion of
pieces into sphinx generated docs to prevent duplication of same
information in multiple places.

Change-Id: I834d4dcf5d9e0bede3840812eb12e1d670421cc5

README.rst

@@ -1,5 +1,8 @@
+README
+======
+
 What is git-upstream?
-=====================
+---------------------
 
 git-upstream is an open source Python application that can be used to
 keep in sync with upstream open source projects, mainly OpenStack.
@@ -80,7 +83,7 @@ automatically dropped, also useful to drop the additional ported changes
 automatically if possible, rather than have it cause conflicts.
 
 What git-upstream is not
-========================
+------------------------
 
 The name of this tool includes the "git-" prefix because of the Git
 naming convention that a Git subcommand must have. So, as git-review
@@ -92,8 +95,8 @@ strictly related to git-review. In other words, git-review can (and most
 of the time will) be used without even knowing about git-upstream
 existence.
 
-git-upstream installation
-=========================
+Installation
+============
 
 At the time of writing, there are two ways to install git-upstream:
 cloning its git repository or using pip.

doc/source/index.rst

@@ -6,6 +6,9 @@
 Welcome to git-upstream's documentation!
 ========================================
 
+.. include:: ../../README.rst
+   :start-after: ======
+   :end-before: git-upstream installation
 
 Contents:
 =========