fixed link to FSLVIEW tutorial

doc/fdt_display.html

@@ -9,6 +9,6 @@ possible to display these vectors using <b>RGB</b> coding (where the colours
 red,green and blue represent diffusion in the x,y,z axes respectively) or
 using <b>lines</b> where a line at each voxel represent the principle
 diffusion direction at that voxel.  For more details see the relevant fslview
-<a href="http://www.fmrib.ox.ac.uk/fsl/fslview/dti_tutorial.html"
+<a href="http://www.fmrib.ox.ac.uk/fsl/fslview/dti.html"
 target="_top">tutorial</a>.