Add proper install instructions

Author: phinate

README.md

@@ -7,6 +7,12 @@
 ![](training.gif)
 
 ## Install
+To use `neos` right now, you have to seperately install the `fax` library for fixed-point differentiation:
+
+`pip install git+https://github.com/gehring/fax.git`
+
+Then just run
+
 `pip install neos`
 
 ## How to use (and reproduce the results from the cool animation)

docs/index.html

@@ -38,7 +38,10 @@
 </div>
 <div class="cell border-box-sizing text_cell rendered"><div class="inner_cell">
 <div class="text_cell_render border-box-sizing rendered_html">
-<h2 id="Install">Install<a class="anchor-link" href="#Install">&#182;</a></h2><p><code>pip install neos</code></p>
+<h2 id="Install">Install<a class="anchor-link" href="#Install">&#182;</a></h2><p>To use <code>neos</code> right now, you have to seperately install the <code>fax</code> library for fixed-point differentiation:</p>
+<p><code>pip install git+https://github.com/gehring/fax.git</code></p>
+<p>Then just run</p>
+<p><code>pip install neos</code></p>
 
 </div>
 </div>