Bump version to add @jlouis666's dialyzer patch

CHANGES

@@ -1,3 +1,7 @@
+In 3.1.1:
+
+* It dialyzes happily now
+
 In 3.1.0:
 
 * Deal with int4range type.

src/epgsql.app.src

@@ -1,6 +1,6 @@
 {application, epgsql,
  [{description, "PostgreSQL Client"},
-  {vsn, "3.1.0"},
+  {vsn, "3.1.1"},
   {modules, []},
   {registered, []},
   {applications, [kernel,