Added unit test project to main solution file.

Avalonia.sln

@@ -1,4 +1,4 @@
-Microsoft Visual Studio Solution File, Format Version 12.00
+Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
 VisualStudioVersion = 15.0.27130.2027
 MinimumVisualStudioVersion = 10.0.40219.1
@@ -193,6 +193,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.Build.Tasks", "src
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "_build", "nukebuild\_build.csproj", "{3F00BC43-5095-477F-93D8-E65B08179A00}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.Animation.UnitTests", "tests\Avalonia.Animation.UnitTests\Avalonia.Animation.UnitTests.csproj", "{AF227847-E65C-4BE9-BCE9-B551357788E0}"
+EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution
 		src\Shared\RenderHelpers\RenderHelpers.projitems*{3c4c0cb4-0c0f-4450-a37b-148c84ff905f}*SharedItemsImports = 13
@@ -1720,6 +1722,30 @@ Global
 		{BF28998D-072C-439A-AFBB-2FE5021241E0}.Release|iPhone.Build.0 = Release|Any CPU
 		{BF28998D-072C-439A-AFBB-2FE5021241E0}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
 		{BF28998D-072C-439A-AFBB-2FE5021241E0}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Ad-Hoc|Any CPU.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Ad-Hoc|Any CPU.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Ad-Hoc|iPhone.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Ad-Hoc|iPhone.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Ad-Hoc|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Ad-Hoc|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.AppStore|Any CPU.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.AppStore|Any CPU.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.AppStore|iPhone.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.AppStore|iPhone.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.AppStore|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.AppStore|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Debug|iPhone.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Debug|iPhone.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Debug|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Debug|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Release|iPhone.ActiveCfg = Release|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Release|iPhone.Build.0 = Release|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
+		{AF227847-E65C-4BE9-BCE9-B551357788E0}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -1773,6 +1799,7 @@ Global
 		{E1240B49-7B4B-4371-A00E-068778C5CF0B} = {C5A00AC3-B34C-4564-9BDD-2DA473EF4D8B}
 		{D49233F8-F29C-47DD-9975-C4C9E4502720} = {E870DCD7-F46A-498D-83FC-D0FD13E0A11C}
 		{3C471044-3640-45E3-B1B2-16D2FF8399EE} = {E870DCD7-F46A-498D-83FC-D0FD13E0A11C}
+		{AF227847-E65C-4BE9-BCE9-B551357788E0} = {C5A00AC3-B34C-4564-9BDD-2DA473EF4D8B}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {87366D66-1391-4D90-8999-95A620AD786A}