Update README.md and add analytics. (#4537)

README.md

@@ -5,27 +5,24 @@
 [![codecov](https://codecov.io/gh/LLNL/spack/branch/develop/graph/badge.svg)](https://codecov.io/gh/LLNL/spack)
 [![Read the Docs](https://readthedocs.org/projects/spack/badge/?version=latest)](https://spack.readthedocs.io)
 
-Spack is a package management tool designed to support multiple
-versions and configurations of software on a wide variety of platforms
-and environments. It was designed for large supercomputing centers,
-where many users and application teams share common installations of
-software on clusters with exotic architectures, using libraries that
-do not have a standard ABI. Spack is non-destructive: installing a new
-version does not break existing installations, so many configurations
-can coexist on the same system.
-
-Most importantly, Spack is simple. It offers a simple spec syntax so
-that users can specify versions and configuration options
-concisely. Spack is also simple for package authors: package files are
-written in pure Python, and specs allow package authors to write a
-single build script for many different builds of the same package.
+Spack is a multi-platform package manager that builds and installs
+multiple versions and configurations of software. It works on Linux,
+macOS, and many supercomputers. Spack is non-destructive: installing a
+new version of a package does not break existing installations, so many
+configurations of the same package can coexist.
+
+Spack offers a simple "spec" syntax that allows users to specify versions
+and configuration options. Package files are written in pure Python, and
+specs allow package authors to write a single script for many different
+builds of the same package.  With Spack, you can build your software
+*all* the ways you want to.
 
 See the
 [Feature Overview](http://spack.readthedocs.io/en/latest/features.html)
 for examples and highlights.
 
-To install spack and install your first package, make sure you have
-Python (2 or 3).  Then:
+To install spack and your first package, make sure you have Python.
+Then:
 
     $ git clone https://github.com/llnl/spack.git
     $ cd spack/bin
@@ -37,15 +34,16 @@ Documentation
 [**Full documentation**](http://spack.readthedocs.io/) for Spack is
 the first place to look.
 
-We've also got a [**Spack 101 Tutorial**](http://spack.readthedocs.io/en/latest/tutorial_sc16.html),
-so you can learn Spack yourself, or teach users at your own site.
+Try the
+[**Spack Tutorial**](http://spack.readthedocs.io/en/latest/tutorial.html),
+to learn how to use spack, write packages, or deploy packages for users
+at your site.
 
 See also:
   * [Technical paper](http://www.computer.org/csdl/proceedings/sc/2015/3723/00/2807623.pdf) and
     [slides](https://tgamblin.github.io/files/Gamblin-Spack-SC15-Talk.pdf) on Spack's design and implementation.
   * [Short presentation](https://tgamblin.github.io/files/Gamblin-Spack-Lightning-Talk-BOF-SC15.pdf) from the *Getting Scientific Software Installed* BOF session at Supercomputing 2015.
 
-
 Get Involved!
 ------------------------
 
@@ -55,9 +53,8 @@ packages to bugfixes, or even new core features.
 
 ### Mailing list
 
-If you are interested in contributing to spack, the first step is to
-join the mailing list.  We're using a Google Group for this, and you
-can join it here:
+If you are interested in contributing to spack, the first step is to join
+the mailing list.  We're Google Groups for this. Join here:
 
   * [Spack Google Group](https://groups.google.com/d/forum/spack)
 
@@ -69,23 +66,22 @@ When you send your request, make ``develop`` the destination branch on the
 [Spack repository](https://github.com/LLNL/spack).
 
 Your PR must pass Spack's unit tests and documentation tests, and must be
-[PEP 8](https://www.python.org/dev/peps/pep-0008/) compliant.
-We enforce these guidelines with [Travis CI](https://travis-ci.org/LLNL/spack).
-To run these tests locally, and for helpful tips on git, see our
+[PEP 8](https://www.python.org/dev/peps/pep-0008/) compliant.  We enforce
+these guidelines with [Travis CI](https://travis-ci.org/LLNL/spack).  To
+run these tests locally, and for helpful tips on git, see our
 [Contribution Guide](http://spack.readthedocs.io/en/latest/contribution_guide.html).
 
-Spack uses a rough approximation of the [Git
-Flow](http://nvie.com/posts/a-successful-git-branching-model/)
+Spack uses a rough approximation of the
+[Git Flow](http://nvie.com/posts/a-successful-git-branching-model/)
 branching model.  The ``develop`` branch contains the latest
-contributions, and ``master`` is always tagged and points to the
-latest stable release.
-
+contributions, and ``master`` is always tagged and points to the latest
+stable release.
 
 Authors
 ----------------
 Many thanks go to Spack's [contributors](https://github.com/llnl/spack/graphs/contributors).
 
-Spack was originally written by Todd Gamblin, tgamblin@llnl.gov.
+Spack was created by Todd Gamblin, tgamblin@llnl.gov.
 
 ### Citing Spack
 
@@ -102,3 +98,5 @@ Spack is released under an LGPL license.  For more details see the
 LICENSE file.
 
 ``LLNL-CODE-647188``
+
+![Analytics](https://ga-beacon.appspot.com/UA-101208306-3/welcome-page?pixel)