add support for ugoira

add progress bar

src/ext/json.rs

@@ -0,0 +1,35 @@
+use json::JsonValue;
+
+pub trait ToJson {
+    fn to_json(&self) -> Option<JsonValue>;
+}
+
+impl ToJson for &str {
+    fn to_json(&self) -> Option<JsonValue> {
+        Some(JsonValue::String(String::from(*self)))
+    }
+}
+
+impl ToJson for &String {
+    fn to_json(&self) -> Option<JsonValue> {
+        Some(JsonValue::String((*self).to_string()))
+    }
+}
+
+impl ToJson for String {
+    fn to_json(&self) -> Option<JsonValue> {
+        Some(JsonValue::String(self.to_string()))
+    }
+}
+
+impl ToJson for JsonValue {
+    fn to_json(&self) -> Option<JsonValue> {
+        Some(self.clone())
+    }
+}
+
+impl ToJson for &JsonValue {
+    fn to_json(&self) -> Option<JsonValue> {
+        Some((*self).clone())
+    }
+}