Update linux docs to use virtualenv (anki#183)

docs/source/install-linux.rst

@@ -13,33 +13,58 @@ This guide provides instructions on installing the Cozmo SDK for computers runni
   * Android command-line tools (https://developer.android.com/studio/index.html#Other)
   * usbmuxd for iOS / :ref:`adb` for Android
 
-^^^^^^^^^^^^^^^^^^^
-Python Installation
-^^^^^^^^^^^^^^^^^^^
 
-""""""""""""
+^^^^^^^^^^^^
 Ubuntu 14.04
-""""""""""""
+^^^^^^^^^^^^
+
+"""""""""""""""""""
+Python Installation
+"""""""""""""""""""
 
 1. Type the following into your Terminal window to install Python 3.5::
 
-    sudo add-apt-repository ppa:fkrull/deadsnakes
+    sudo add-apt-repository ppa:deadsnakes
     sudo apt-get update
-    sudo apt-get install python3.5
-    sudo update-alternatives --install /usr/bin/python3 python3.5 /usr/bin/python3.5 99
+    sudo apt-get install python3.5 python3.5-tk
 
-2. Then install pip by typing in the following into the Terminal window::
+2. Then, install and set up virtualenv::
 
-    sudo apt-get install python3-setuptools
-    sudo easy_install3 pip
+    sudo apt-get install python-pip
+    pip install virtualenv
+    virtualenv -p python3.5 ~/cozmo-env
 
-3. Last, install Tkinter::
+3. Last, make sure to activate the virtualenv any time you use cozmo::
+
+    source ~/cozmo-env/bin/activate
+
+.. note:: You'll need to activate the virtualenv before running any python or pip commands.  Learn more about virtualenv `here <https://virtualenv.pypa.io/en/stable/userguide/>`_.
+
+""""""""""""""""
+SDK Installation
+""""""""""""""""
+
+To install the SDK, type the following into the Terminal window::
+
+    pip install 'cozmo[camera]'
+
+Note that the [camera] option adds support for processing images from Cozmo's camera.
+
+"""""""""""
+SDK Upgrade
+"""""""""""
+
+To upgrade the SDK from a previous install, enter this command::
 
-    sudo apt-get install python3.5-tk
+    pip install --upgrade cozmo
 
-""""""""""""
+^^^^^^^^^^^^
 Ubuntu 16.04
-""""""""""""
+^^^^^^^^^^^^
+
+"""""""""""""""""""
+Python Installation
+"""""""""""""""""""
 
 1. Type the following into your Terminal window to install Python::
 
@@ -54,9 +79,9 @@ Ubuntu 16.04
 
     sudo apt-get install python3-pil.imagetk
 
-^^^^^^^^^^^^^^^^
+""""""""""""""""
 SDK Installation
-^^^^^^^^^^^^^^^^
+""""""""""""""""
 
 To install the SDK, type the following into the Terminal window::