Replaced NotImplementedException for streams

Especially for streams, it is more appropriate to throw
NotSupportedException instead of NotImplementedException. Usually
consumers of streams expect NotSupportedException to handle errors.
There are other places that also use NotImplementedException but I
didn't examine them for now. I only modified stream classes in
SharpCompress.IO. For reference about this best practise, please see
these articles:
http://blogs.msdn.com/b/brada/archive/2004/07/29/201354.aspx

http://blogs.msdn.com/b/jaredpar/archive/2008/12/12/notimplementedexception-vs-notsupportedexception.aspx

SharpCompress/IO/CountingWritableSubStream.cs

@@ -35,28 +35,28 @@ namespace SharpCompress.IO
 
         public override long Length
         {
-            get { throw new NotImplementedException(); }
+            get { throw new NotSupportedException(); }
         }
 
         public override long Position
         {
-            get { throw new NotImplementedException(); }
-            set { throw new NotImplementedException(); }
+            get { throw new NotSupportedException(); }
+            set { throw new NotSupportedException(); }
         }
 
         public override int Read(byte[] buffer, int offset, int count)
         {
-            throw new NotImplementedException();
+            throw new NotSupportedException();
         }
 
         public override long Seek(long offset, SeekOrigin origin)
         {
-            throw new NotImplementedException();
+            throw new NotSupportedException();
         }
 
         public override void SetLength(long value)
         {
-            throw new NotImplementedException();
+            throw new NotSupportedException();
         }
 
         public override void Write(byte[] buffer, int offset, int count)