title: Postgres.app says "Running on Port 5432" but psql command fails
body: <p>I installed Postgres.app, and when I open it, the menu bar icon says "Running on Port 5432". But when I click on the "Open psql" menu option, I see the following message:</p>
  
  <pre><code>/Applications/Postgres.app/Contents/MacOS/bin/psql ; exit;
  psql: could not connect to server: No such file or directory
  Is the server running locally and accepting
  connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
  logout
  
  [Process completed]
  </code></pre>
  
  <p>Any ideas what might be up?</p>