Automatically assign property/fields values from the source to the destination instance

This Pull Request improves the `CreateProxy` method so that it can automatically assign property/fields values from the *source* to the *destination* instance.

Originally, the `CreateProxy` method did not copy any values to the destination instance. Once the proxy has been created, one had to manually assign the property values and then do the comparison.

Tracked issue: [#87](https://github.com/AutoFixture/AutoFixture/issues/87)