Fix unit tests after #58.

- Moving package down in sources collection wasn't working.
- Remove --no-build from Run-Tests.ps1, because we don't build whole solution in previous steps.

Author: maraf

src/PackageManager.NuGet/Models/NuGetPackageSourceCollection.cs

@@ -107,7 +107,7 @@ public int MoveDown(IPackageSource source)
             {
                 Sources.RemoveAt(index);
                 Sources.Insert(++index, target);
-                SavePackageSources();
+                SavePackageSources(true);
             }
 
             return index;

tools/Run-Tests.ps1

@@ -1,6 +1,6 @@
 Push-Location $PSScriptRoot;
 
-dotnet test ..\test\PackageManager.NuGet.Tests\PackageManager.NuGet.Tests.csproj -c Release --no-build --test-adapter-path:.. --logger:Appveyor /property:Platform=AnyCPU
-dotnet test ..\test\PackageManager.Tests\PackageManager.Tests.csproj -c Release --no-build --test-adapter-path:.. --logger:Appveyor /property:Platform=AnyCPU
+dotnet test ..\test\PackageManager.NuGet.Tests\PackageManager.NuGet.Tests.csproj -c Release --test-adapter-path:.. --logger:Appveyor /property:Platform=AnyCPU
+dotnet test ..\test\PackageManager.Tests\PackageManager.Tests.csproj -c Release --test-adapter-path:.. --logger:Appveyor /property:Platform=AnyCPU
 
 Pop-Location;