Implemented Single threaded Dispatcher,wrote test cases

I've implemented single thread dispatcher. If this is correct then I'll update it to concurrent version which I've started. I just wanted to confirm my approach.
One refactoring that you could potentially do is maintain a list of extensions for a particular handler.
It might make the configuration a bit more concise.
Example:
```xml
<handlers>
    <handler type="staticHandler" extensions="css | html | js | png" />
   ...
</handler>
```