Fix some Dart 2 runtime test errors (#92)

Partially addresses #57
diff --git a/pubspec.yaml b/pubspec.yaml
index 7e00af0..d3bec8b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -6,7 +6,7 @@
 
 environment:
   # Required for Dart 2.0 collection changes.
-  sdk: '>=2.0.0-dev.22.0 <2.0.0'
+  sdk: '>=2.0.0-dev.36.0 <2.0.0'
 
 dev_dependencies:
   build_runner: ^0.8.0
diff --git a/test/union_set_controller_test.dart b/test/union_set_controller_test.dart
index 366b781..8c561d3 100644
--- a/test/union_set_controller_test.dart
+++ b/test/union_set_controller_test.dart
@@ -7,11 +7,11 @@
 import "package:collection/collection.dart";
 
 void main() {
-  var controller;
+  UnionSetController<int> controller;
   Set<int> innerSet;
   setUp(() {
     innerSet = new Set.from([1, 2, 3]);
-    controller = new UnionSetController<int>()..add(innerSet);
+    controller = new UnionSetController()..add(innerSet);
   });
 
   test("exposes a union set", () {
diff --git a/test/union_set_test.dart b/test/union_set_test.dart
index f2a792a..d0437ff 100644
--- a/test/union_set_test.dart
+++ b/test/union_set_test.dart
@@ -42,10 +42,10 @@
   group("with multiple disjoint sets", () {
     var set;
     setUp(() {
-      set = new UnionSet<int>.from([
-        new Set.from([1, 2]),
-        new Set.from([3, 4]),
-        new Set.from([5]),
+      set = new UnionSet.from([
+        new Set.of([1, 2]),
+        new Set.of([3, 4]),
+        new Set.of([5]),
         new Set()
       ], disjoint: true);
     });
@@ -81,10 +81,10 @@
   group("with multiple overlapping sets", () {
     var set;
     setUp(() {
-      set = new UnionSet<int>.from([
-        new Set.from([1, 2, 3]),
-        new Set.from([3, 4]),
-        new Set.from([5, 1]),
+      set = new UnionSet.from([
+        new Set.of([1, 2, 3]),
+        new Set.of([3, 4]),
+        new Set.of([5, 1]),
         new Set()
       ]);
     });
@@ -114,8 +114,8 @@
       expect(duration1, isNot(same(duration2)));
 
       var set = new UnionSet.from([
-        new Set.from([duration1]),
-        new Set.from([duration2])
+        new Set.of([duration1]),
+        new Set.of([duration2])
       ]);
 
       expect(set.lookup(new Duration(seconds: 0)), same(duration1));
@@ -134,10 +134,10 @@
   group("after an inner set was modified", () {
     var set;
     setUp(() {
-      var innerSet = new Set<int>.from([3, 7]);
-      set = new UnionSet<int>.from([
-        new Set.from([1, 2]),
-        new Set.from([5]),
+      var innerSet = new Set.of([3, 7]);
+      set = new UnionSet.from([
+        new Set.of([1, 2]),
+        new Set.of([5]),
         innerSet
       ]);
 
@@ -178,16 +178,16 @@
   group("after the outer set was modified", () {
     var set;
     setUp(() {
-      var innerSet = new Set.from([6]);
-      var outerSet = new Set<Set<int>>.from([
-        new Set.from([1, 2]),
-        new Set.from([5]),
+      var innerSet = new Set.of([6]);
+      var outerSet = new Set.of([
+        new Set.of([1, 2]),
+        new Set.of([5]),
         innerSet
       ]);
 
       set = new UnionSet<int>(outerSet);
       outerSet.remove(innerSet);
-      outerSet.add(new Set.from([3, 4]));
+      outerSet.add(new Set.of([3, 4]));
     });
 
     test("length returns the total length", () {