Updates README.md to include setup instrutions

Author: freespace

README.md

@@ -1,7 +1,10 @@
 pyAPT
 =====
 
-Python interface to Thorlab's APT motion controllers. Depends on `libftdi1` and `pylibftdi`.
+Python interface to Thorlab's APT motion controllers. Depends on `libftdi1` and
+`pylibftdi`. Under Linux the easiest way to get these is to install `libftdi1`
+using the package management system, and then install `pylibftdi` into a virtual
+environment or equivalent.
 
 Development is ongoing, and I will be adding functionality as I need them in
 the course of my DPhil.