Add better typed duration and ratio properties

src/lib/Ppvm.vala

@@ -85,21 +85,33 @@ namespace Ppub {
             }
         }
     
-        public string? ratio {
+        public double[]? ratio {
             owned get {
-                return get_value(RATIO);
+                var ratio = get_value(RATIO);
+                if(ratio == null) {
+                    return null;
+                }
+                var ratio_data = ratio.split(":", 2);
+                return new double[] {
+                    double.parse(ratio_data[0]),
+                    double.parse(ratio_data[1])
+                };
             }
             set {
-                set_value(RATIO, value);
+                set_value(RATIO, @"$(value[0]):$(value[1])");
             }
         }
     
-        public string? duration {
+        public double? duration {
             owned get {
-                return get_value(DURATION);
+                var duration = get_value(DURATION);
+                if(duration == null) {
+                    return null;
+                }
+                return double.parse(duration);
             }
             set {
-                set_value(DURATION, value);
+                set_value(DURATION, value.to_string());
             }
         }