add mamba instructions and refine installation quick start

pages/installation_quick_start.md

@@ -4,69 +4,52 @@ title: Installation Quick Start
 order: 2
 ---
 
-MDAnalysis offers multiple installation methods. For most
-users we recommend [mamba][] installation method, a faster
-drop-in replacement for [conda][] .
+MDAnalysis can be installed using [mamba][] (recommended) or [pip][].
 
 ## Mamba ##
 
-If you don't have [conda][] installed yet, follow the [installation
-instructions for conda][]. Following that, install [mamba][] with:
+If you have [conda][] or [mamba][] installed, run:
 
 {% highlight bash %}
 conda install -c conda-forge mamba
-{% endhighlight %}
-
-Then, install the latest stable release of MDAnalysis with:
-
-{% highlight bash %}
 mamba install -c conda-forge mdanalysis
 {% endhighlight %}
 
-To upgrade use:
-
-{% highlight bash %}
-mamba update mdanalysis
-{% endhighlight %}
-
-To [run the test cases][run_tests] and examples, also install the unit tests (about 90 MB
-in size):
+To install [test cases][] cases (about 90 MB
+in size) run: 
 
 {% highlight bash %}
 mamba install -c conda-forge MDAnalysisTests
 {% endhighlight %}
 
-MDAnalysis installed via mamba supports only serial calculations. 
-If you need OpenMP-based parallelism, install MDAnalysis via [pip](#python-package-index) 
-and ensure you have a working [OpenMP][] installation.
+MDAnalysis via [mamba][] supports only serial calculations. 
+For OpenMP-based parallelism, use [pip][] and ensure you have 
+a working [OpenMP][] installation.
 
 ## Python Package Index ##
 
-To install the latest stable release with
-[pip][pip] (which should be available in all Python installations) do:
+To install with [pip][] run:
 
 {% highlight bash %}
 pip install --upgrade MDAnalysis
 {% endhighlight %}
 
-To [run the test cases][run_tests] and examples, also install the unit tests (about 53 MiB
-in size):
+To install [test cases][] run:
 
 {% highlight bash %}
 pip install --upgrade MDAnalysisTests
 {% endhighlight %}
 
 ## More ##
 
-For more installation options and additional details see [Installing
-MDAnalysis in the {{ site.docs.userguide.name }}]({{ site.docs.userguide.url }}/stable/installation.html).
+For detailed installation methods, including setting up [mamba][] from scratch, see the [Installation instuctions in the {{ site.docs.userguide.name }}]({{ site.docs.userguide.url }}/stable/installation.html).
 
-If you have questions with the installation, please ask on
+If you have questions regarding the installation, please ask on
 [{{site.mailinglists.discussion.name}}]({{site.mailinglists.discussion.url}}).
 
 [pip]: https://pip.pypa.io/en/latest/
 [mamba]:https://anaconda.org/conda-forge/mamba
 [conda]: https://conda.io/
-[installation instructions for conda]: https://conda.io/projects/conda/en/latest/user-guide/install/index.html
+[installation instuctions]: https://mamba.readthedocs.io/en/latest/installation/mamba-installation.html
 [OpenMP]: https://www.openmp.org/
-[run_tests]: {{ site.docs.userguide.url }}/stable/installation.html#testing
+[test cases]: {{ site.docs.userguide.url }}/stable/installation.html#testing