Installation issues

Resolves the following:

- #351 (use of `sudo` when installing)
- #420 (failure to install on Windows)
- #431 (failure to install on MacOS)

Application now relies on `appdirs` module to identify the appropriate
locations for storing configuration and data, both during installation
and runtime.

Vagrantfile

@@ -8,10 +8,13 @@ Vagrant.configure("2") do |config|
     vb.memory = "512"
   end
 
-  config.vm.provision "shell", inline: <<-SHELL
+  config.vm.provision "shell", privileged: false, inline: <<-SHELL
      sudo apt-get update
      sudo apt-get install -y python-pip
-     su vagrant && sudo -H pip install docopt pygments termcolor flake8
-     cd /vagrant && sudo python setup.py install
+     sudo -H pip install flake8
+     pip install --user docopt pygments termcolor
+     cd /vagrant/ && python setup.py install --user
+     echo 'export PATH=$PATH:/home/vagrant/.local/bin' >> /home/vagrant/.bashrc
   SHELL
+
 end