fix net451 issues

Author: DaniilSokolyuk

src/React.Sample.Mvc4/React.Sample.Mvc4.csproj

@@ -92,7 +92,7 @@
     <Reference Include="System.Web" />
     <Reference Include="System.Web.Abstractions" />
     <Reference Include="System.Web.Optimization.React">
-      <HintPath>..\System.Web.Optimization.React\bin\$(Configuration)\net40\System.Web.Optimization.React.dll</HintPath>
+      <HintPath>..\System.Web.Optimization.React\bin\$(Configuration)\net451\System.Web.Optimization.React.dll</HintPath>
     </Reference>
     <Reference Include="System.Web.Routing" />
     <Reference Include="System.Xml" />

src/React.Sample.Mvc4/TransformBabel.proj

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="TransformBabel">    
-	<UsingTask AssemblyFile="..\React.MSBuild\bin\$(Configuration)\net40\React.MSBuild.dll" TaskName="TransformBabel" />
+	<UsingTask AssemblyFile="..\React.MSBuild\bin\$(Configuration)\net451\React.MSBuild.dll" TaskName="TransformBabel" />
 	<Target Name="TransformBabel">
 		<TransformBabel SourceDir="$(MSBuildProjectDirectory)" />
 	</Target>