(GH-231) nupkg should be created in current directory

When running choco pack, the resulting nupkg used to be created in the current
directory and not necessarily in the same directory as the nuspec file. The
previous behavior is preferred. Allow for the package to be created in the
current working directory instead of the nuspec directory.

src/chocolatey/infrastructure.app/services/NugetService.cs

@@ -160,7 +160,7 @@ public void pack_run(ChocolateyConfiguration config)
             }
 
             string outputFile = builder.Id + "." + builder.Version + Constants.PackageExtension;
-            string outputPath = _fileSystem.combine_paths(nuspecDirectory, outputFile);
+            string outputPath = _fileSystem.combine_paths(_fileSystem.get_current_directory(), outputFile);
 
             this.Log().Info(() => "Attempting to build package from '{0}'.".format_with(_fileSystem.get_file_name(nuspecFilePath)));