Solution folders get parsed as CsProjFile

## Scenario

Existing solution that uses folders to group project files:

```
+
 |-- Data (folder)
         |--- Repository (csproj)

```

Solution is parsed using `Solution.LoadFrom`

| Assertion | Expected | Actual |
| :-- | --- | --- |
| `Solution.Projects.Count()` | 1 | 2 |
## Question

Is this expected behavior? If not I'll submit a pull request to filter out the folders. 
