Improves documentation. (#44)

* Adds system requirements.
* References our mailing list.
* Nudges folks toward using ROS.

README.rst

@@ -30,13 +30,14 @@ configurations.
 .. _Cartographer: https://github.com/googlecartographer/cartographer
 .. _SLAM: https://en.wikipedia.org/wiki/Simultaneous_localization_and_mapping
 
-Documentation
-=============
+Getting started
+===============
 
-You will find complete documentation for using Cartographer at `our Read the
-Docs site`_.
+* Learn to use Cartographer at `our Read the Docs site`_.
+* Please join the `mailing list`_ and ask questions.
 
 .. _our Read the Docs site: https://google-cartographer.readthedocs.io
+.. _mailing list: https://groups.google.com/forum/#!forum/google-cartographer
 
 Contributing
 ============
@@ -50,12 +51,10 @@ page`_.
     :alt: Build Status
     :scale: 100%
     :target: https://travis-ci.org/googlecartographer/cartographer
-
 .. |docs| image:: https://readthedocs.org/projects/google-cartographer/badge/?version=latest
     :alt: Documentation Status
     :scale: 100%
     :target: https://google-cartographer.readthedocs.io/en/latest/?badge=latest
-
 .. |video| image:: https://j.gifs.com/wp3BJM.gif
     :alt: Cartographer 3D SLAM Demo
     :scale: 100%

docs/source/index.rst

@@ -27,8 +27,14 @@ configurations.
 .. _Cartographer: https://github.com/googlecartographer/cartographer
 .. _SLAM: https://en.wikipedia.org/wiki/Simultaneous_localization_and_mapping
 
+Getting started
+===============
+
+Cartographer is a standalone C++ library. To get started quickly, use our `ROS
+<http://www.ros.org>`_ integration.
+
 Getting started with ROS
-========================
+------------------------
 
 ROS integration is provided by the `Cartographer ROS repository`_. You will find
 complete documentation for using Cartographer with ROS at the
@@ -38,7 +44,10 @@ complete documentation for using Cartographer with ROS at the
 .. _Cartographer ROS Read the Docs site: https://google-cartographer-ros.readthedocs.io
 
 Getting started without ROS
-===========================
+---------------------------
+
+Please see our ROS integration as a starting point for integrating your system
+with the standalone library. Currently, it is the best available reference.
 
 On Ubuntu 14.04 (Trusty):
 
@@ -57,6 +66,17 @@ On Ubuntu 14.04 (Trusty):
   :linenos:
   :lines: 20-
 
+System Requirements
+===================
+
+Although Cartographer may run on other systems, it is confirmed to be working
+on systems that meet the following requirements:
+
+* 64-bit, modern CPU (e.g. 3rd generation i7)
+* 16 GB RAM
+* Ubuntu 14.04 (Trusty)
+* gcc version 4.8.4
+
 How to cite us
 ==============