Add libpq-dev as a dependency

README.md

@@ -29,9 +29,10 @@ the project):
 
 
 Install dependencies. On Debian, you will probably need the
-`python-dev`, `python-pip`, `libldap-dev` and `libsasl2-dev` packages.
+`python-dev`, `python-pip`, `libldap-dev`, `libpq-dev` and `libsasl2-dev`
+packages.
 
-sudo apt-get install python-dev python-pip libldap2-dev libsasl2-dev
+  sudo apt-get install python-dev python-pip libldap2-dev libpq-dev libsasl2-dev
 
 Then run: