add installation instruction for arch linux

content/install.txt

@@ -4,8 +4,8 @@ Downloading and installing Kwant
 
 The quickest and easiest way to install Kwant is using the prepared packages
 that are available for `Windows`_, GNU/Linux (`Debian
-<#debian-and-derivatives>`_ or `Ubuntu <#ubuntu-and-derivatives>`_, and their
-variants), and `Mac OS X`_.  It is possible to be notified about new releases
+<#debian-and-derivatives>`_, `Ubuntu <#ubuntu-and-derivatives>`_, and their
+variants, `Arch Linux`_), and `Mac OS X`_.  It is possible to be notified about new releases
 of Kwant through an `announcement mailing list
 <community.html#announcements-of-new-releases>`_.
 
@@ -107,6 +107,15 @@ This method should work for virtually all Debian-derived systems, even on exotic
 architectures.
 
 
+Arch Linux
+==========
+
+`Arch install scripts for Kwant
+<https://aur.archlinux.org/packages/python2-kwant/>`_ are available.  To
+install, follow the `Arch User Repository installation instructions
+<https://wiki.archlinux.org/index.php/Arch_User_Repository#Installing_packages>`_.
+
+
 Mac OS X
 ========