Clean repo

Cleaned up version of the codebase for review.
The 6-7 lines above are a good example of feature jealousy.
Its when one type is jealous of another type and wants to do something that they other type would be better suited for doing.
In this example, since the mime type lookup depends only on the internal state of the mime mapping, it would be a function exposed directly via the MimeMapping class. 
Example:
```csharp
// The GetMappingOrDefault() internally reads the dictionary and returns the found mapping or a
// default mapping of application/octet-stream incase no explicit mime mapping is found.
var mimeType = mimeMapping.GetMappingOrDefault(extension);
```