allow uppercase meridian to be valid

lib/validates_timeliness/formats.rb

@@ -123,7 +123,7 @@ module ValidatesTimeliness
       { 'ss'   => [ /s{2,}/, '(\d{2})',   :sec ] },
       { 's'    => [ /s{1}/,  '(\d{1,2})', :sec ] },
       { 'u'    => [ /u{1,}/, '(\d{1,6})', :usec ] },
-      { 'ampm' => [ /ampm/,  '((?:a|p)\.?m\.?)', :meridian ] },
+      { 'ampm' => [ /ampm/,  '((?:[aApP])\.?[mM]\.?)', :meridian ] },
       { 'zo'   => [ /zo/,    '(?:[+-]\d{2}:?\d{2})'] },
       { 'tz'   => [ /tz/,    '(?:[A-Z]{1,4})' ] }, 
       { '_'    => [ /_/,     '\s?' ] }