Fix bindings not being unsubscribed on Dispose.

src/Perspex.Base/PriorityLevel.cs

@@ -140,6 +140,7 @@ namespace Perspex
             return Disposable.Create(() =>
             {
                 Bindings.Remove(node);
+                entry.Dispose();
 
                 if (entry.Index >= ActiveBindingIndex)
                 {

tests/Perspex.Base.UnitTests/PerspexObjectTests_Binding.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Reactive.Linq;
 using System.Reactive.Subjects;
+using Microsoft.Reactive.Testing;
 using Perspex.Data;
 using Xunit;
 
@@ -81,6 +82,22 @@ namespace Perspex.Base.UnitTests
             Assert.Equal("foodefault", target.GetValue(Class1.FooProperty));
         }
 
+        [Fact]
+        public void Observable_Is_Unsubscribed_When_Subscription_Disposed()
+        {
+            var scheduler = new TestScheduler();
+            var source = scheduler.CreateColdObservable<object>();
+            var target = new Class1();
+
+            var subscription = target.Bind(Class1.FooProperty, source);
+            Assert.Equal(1, source.Subscriptions.Count);
+            Assert.Equal(Subscription.Infinite, source.Subscriptions[0].Unsubscribe);
+
+            subscription.Dispose();
+            Assert.Equal(1, source.Subscriptions.Count);
+            Assert.Equal(0, source.Subscriptions[0].Unsubscribe);
+        }
+
         [Fact]
         public void Two_Way_Separate_Binding_Works()
         {

tests/Perspex.Base.UnitTests/packages.config

@@ -3,6 +3,9 @@
   <package id="Rx-Core" version="2.2.5" targetFramework="net45" />
   <package id="Rx-Interfaces" version="2.2.5" targetFramework="net45" />
   <package id="Rx-Linq" version="2.2.5" targetFramework="net45" />
+  <package id="Rx-Main" version="2.2.5" targetFramework="net45" />
+  <package id="Rx-PlatformServices" version="2.2.5" targetFramework="net45" />
+  <package id="Rx-Testing" version="2.2.5" targetFramework="net45" />
   <package id="Serilog" version="1.5.14" targetFramework="net45" />
   <package id="xunit" version="2.1.0" targetFramework="net45" />
   <package id="xunit.abstractions" version="2.0.0" targetFramework="net45" />