Continuum: Generate distinct Uri objects.

Uris need to, ultimately, be unique, but Continuum creates default
Uri objects which are value-equivalent in Dart.

As an initial solution for text information, use the information
to create a unique Uri.

References #3.

Author: Yong Bakos

lib/src/continuum.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'thing.dart';
 
 /// The whole set of all information.
@@ -19,7 +20,10 @@ class Continuum {
 
   /// Transform `information` into a [Thing] with a URI.
   Thing store(dynamic information) {
-    final thing = Thing(information: information, uri: Uri());
+    final thing = Thing(
+      information: information,
+      uri: Uri.dataFromBytes(utf8.encode(information))
+    );
     things[thing.uri] = thing;
     return thing;
   }