Merge pull request #339 from Bisaloo/patch-1

Update URL to Paul Tol technical note

doc/metropolistheme.dtx

@@ -528,7 +528,7 @@ possible as well as from black and white, can be discerned item under different
 lighting and display environments and by color-blind viewers, while matching
 well together.
 
-In a \href{https://personal.sron.nl/~pault/colourschemes.pdf}{technical note}
+In a \href{https://personal.sron.nl/~pault/data/colourschemes.pdf}{technical note}
 for SRON, Paul Tol proposed a palette of colors satisfying these constraints.
 The sub-package |pgfplotsthemetol| defines palettes for |pgfplots| charts
 based on Tol's work.