Simple problems resolved

Good morning!

I added the files with the solutions.
They were created in Visual Studio 2010.

Here is a print screen of the VS Solution if you want to reproduce it:
![vs_solution](https://cloud.githubusercontent.com/assets/8064846/3478786/0748603c-0344-11e4-9cd8-14a79bd121ac.png)

The UnitTests project needs a reference to the SimpleProblems project.

Thank you for your time.
For the record

```c#
public static int SumEvens(this IEnumerable<int> items)
{
    return items.Where(item => item.IsEven()).Sum();
}
```