Update all dependencies.

* Switch to using kingpin for CLI interface as upstream Prometheus has moved
  that way too.

vendor/github.com/lib/pq/ssl_windows.go

@@ -0,0 +1,9 @@
+// +build windows
+
+package pq
+
+// sslKeyPermissions checks the permissions on user-supplied ssl key files.
+// The key file should have very little access.
+//
+// libpq does not check key file permissions on Windows.
+func sslKeyPermissions(string) error { return nil }