scsi_device.py: Added the <readwrite> parameter.

 * By default, the device is opened read-only.  Passing readwrite=True causes the underlying C code to attempt to open the device read/write.
 * This amended commit cleans up some whitespace mangling that occurred.
Merge branch 'master' of github.com:c-r-h/python-scsi
Fixes some whitespace managling that occurred.
scsi_device.py: Added the <readwrite> parameter.

 * By default, the device is opened read-only.  Passing readwrite=True causes the underlying C code to attempt to open the device read/write.
 * Updated commit removes some whitespace mangling caused by an overzealous text editor.