Update ArchLinux instructions

Stem has been removed from the community maintained AUR repository, and moved to the official ArchLinux repos. As sucn updating our links and installation instructions. [1] https://aur.archlinux.org/packages/stem/ [2] https://www.archlinux.org/packages/community/any/python-stem/

Update ArchLinux instructions
0d09943e · Damian Johnson · 49c6a17a · 0d09943e
Commit 0d09943e authored Nov 18, 2018 by Damian Johnson
--- a/docs/download.rst
+++ b/docs/download.rst
@@ -157,19 +157,16 @@ Download
         % sudo emerge stem

   * - .. image:: /_static/section/download/archlinux.png
-          :target: https://aur.archlinux.org/packages/stem/
+          :target: https://www.archlinux.org/packages/community/any/python-stem/

     - .. image:: /_static/label/archlinux.png
-          :target: https://aur.archlinux.org/packages/stem/
+          :target: https://www.archlinux.org/packages/community/any/python-stem/

-       Package by Sjon for `Arch Linux
-       <https://wiki.archlinux.org/index.php/AUR#Installing_packages>`_.
+       Package by Sjon for `Arch Linux...

       ::

-           % wget https://aur.archlinux.org/cgit/aur.git/snapshot/stem.tar.gz
-           % tar -xvf stem.tar.gz
-           % cd stem; makepkg --install
+           % pacman -S python-stem

   * - .. image:: /_static/section/download/slackware.png
          :target: https://slackbuilds.org/repository/14.2/python/stem/