Merge pull request #2 from randolf/patch-2

Update README.md

Author: okbob

README.md

@@ -32,7 +32,7 @@ Copyright (c) Pavel Stehule ([email protected])
 You will probably need the "postgres.h" source file.  If you're using Debian
 or many other Linux distributions that use aptitude, installation is easy:
 
-    apt install postgres-server-dev-all
+    apt install postgresql-server-dev-all
 
 Installation instructions: