text: Title: When installed via pip, gir1.2-appindicator3-0.1 required
  Body: ## Classification:
  
  UI/Usability
  
  ## Reproducibility:
  
  Always
  
  ## Summary
  
  Attempting to install via pip3 on recent debian has no problem until you attempt to launch the gui.  It depends on the package 
  
  ## Steps to Reproduce
  
  - pip3 install autokey
  - for good measure install libappindicator-3 (and -dev)
  - fix any more missing pip3 dependancies
  - pip3 install autokey
  - autokey-gtk
  
  ## Expected Results
  
  - The gui should start
  
  ## Actual Results
  
  $ autokey-gtk                                                                                                                                                                            (minikube/kube-system)
  Traceback (most recent call last):
    File "/home/ranyardm/.local/bin/autokey-gtk", line 7, in <module>
      from autokey.gtkui.__main__ import main
    File "/home/ranyardm/.local/lib/python3.5/site-packages/autokey/gtkui/__main__.py", line 4, in <module>
      from autokey.gtkapp import Application
    File "/home/ranyardm/.local/lib/python3.5/site-packages/autokey/gtkapp.py", line 31, in <module>
      from autokey.gtkui.notifier import get_notifier
    File "/home/ranyardm/.local/lib/python3.5/site-packages/autokey/gtkui/notifier.py", line 22, in <module>
      gi.require_version('AppIndicator3', '0.1')
    File "/usr/lib/python3/dist-packages/gi/__init__.py", line 118, in require_version
      raise ValueError('Namespace %s not available' % namespace)
  ValueError: Namespace AppIndicator3 not available
  
  If helpful, submit screenshots of the issue to help debug. `autokey-gtk --verbose` output is also useful.
  
  ## Version
  
  0.93.10
  
  If the problem is known to be present in more than one version, please list all of those.
  
  Installed via: pip3 install autokey
  
  Distro:
  
  latest debian (9.4)
  
  Describe any debugging steps you've taken yourself.
  
  Lots of googling, eventually found a solution
  
  If you've found a workaround, provide it here.
  
  apt install gir1.2-appindicator3-0.1
  
  ^^ The above should be in the README.md, the wiki somewhere or somewhere much more obvious than it is.
  
  