Remove commented code (closes #98)

Basic but useful implementation.

Removes basic commented code like

where:

````csharp
            // this comment will be preserved
            // var i = 10;
````

becomes

````csharp
            // this comment will be preserved
````

multiple commented code lines:

where:

````csharp
            // this comment will be preserved
            // if (something)
            // {
            //   DoStuff();
            // }
````

becomes:

````csharp
            // this comment will be preserved
````

some nonvalid code, but...

where 

````csharp
            // this comment will be preserved
            // class Fee
            class Foo
            {
            }
````

becomes

````csharp
            // this comment will be preserved
            class Foo
            {
            }
````

* regular comments are preserved.

I know that, probably, there are a lot of missing things. But, I think this is that kind of feature that needs some use to get improved.