Add missing dependency libjpeg-dev (fixes #45)

README.md

@@ -59,10 +59,10 @@ the project):
 
 
 Install dependencies. On Debian, you will probably need the
-`python-dev`, `python-pip`, `libldap-dev`, `libpq-dev` and `libsasl2-dev`
-packages.
+`python-dev`, `python-pip`, `libldap-dev`, `libpq-dev`, `libsasl2-dev`,
+and `libjpeg-dev` packages.
 
-    sudo apt-get install python-dev python-pip libldap2-dev libpq-dev libsasl2-dev
+    sudo apt-get install python-dev python-pip libldap2-dev libpq-dev libsasl2-dev libjpeg-dev
 
 Then run: