Call to_path on objects passed to IO.copy_stream
Do not close the io's given to copy_stream
Raise IOError if file not readable or writable
Increment from io position by transfer size
Add length and offset args to IO.copy_stream
Merge pull request #466 from atambo/copy_stream_to_path

Bunch of fixes for IO.copy_stream

I will address Wayne's concerns after I merge this.