Update _s.pot : add "Primary Menu" in header.php(L31).
Merge pull request #469 from gatespace/update_s_pot20140428

Update _s.pot : add "Primary Menu" in header.php(L31). And remove 'Menu'.
Merge remote-tracking branch 'upstream/master' into ja

* upstream/master:
  Update _s.pot : add "Primary Menu" in header.php(L31).