Merge pull request #61 from albarin/allow-year-month-dates

Allow dates with the `YYYY-MM` format

src/Parser/Date.php

@@ -34,6 +34,10 @@ public static function parse(\Gedcom\Parser $parser)
             return $dat->getYear().'-'.substr("0{$dat->getMonth()}", -2).'-'.substr("0{$dat->getDay()}", -2);
         }
 
+        if ($dat->getYear() && $dat->getMonth()) {
+            return $dat->getYear().'-'.substr("0{$dat->getMonth()}", -2);
+        }
+
         return $dat->getYear();
     }
 }