Update list of packages to install

I just got the code building on a fresh Jessie install, and those are
what I had to explicitly install.

Change-Id: I88e85a78601c4b9a7b1a0fe092194d743641b1cb
diff --git a/README.md b/README.md
index 74b6a49..530baa8 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@
 	 and put them in `/etc/apt/sources.list.d/`.
   1. Install the required packages:
 ```console
-apt-get install python bazel ruby clang-format-3.5 clang-3.6
+apt-get install python libpython-dev bazel ruby clang-format-3.5 clang-3.6 gfortran libblas-dev liblapack-dev python-scipy python-matplotlib
 ```
   2. Allow Bazel's sandboxing to work