Cleanup installation docs

This PS organizes the installation document tree for easier navigation
and updating relevant content.

Change-Id: I51951d99dfc06bf441bd65ca817119cbca061851

doc/source/install/developer/gates.rst

@@ -0,0 +1 @@
+.. include:: ../../../../tools/gate/README.rst

doc/source/install/developer/index.rst

@@ -1,9 +1,11 @@
-Developer installation
+Development
-======================
+===========
 
 Contents:
 
 .. toctree::
    :maxdepth: 2
 
+   all-in-one
+   gates
    vagrant

doc/source/install/index.rst

@@ -7,6 +7,4 @@ Contents:
    :maxdepth: 2
 
    developer/index
-   all-in-one
    multinode
-   third-party-tools

doc/source/install/third-party-tools.rst

@@ -1,6 +0,0 @@
-=================
-Third-party tools
-=================
-
-Armada
-======

tools/vagrant/README.rst

@@ -2,6 +2,10 @@
 Vagrant Deployment
 ==================
 
+A Vagrantfile has been provided in the ``tools/`` directory.  This
+vagrant installation will prep a single VM with specs from the ``config.rb``
+file, and will run OpenStack-Helm gate scripts to set up Kubernetes.
+
 Requirements
 ------------