Accept ranges in yticks, xticks

Fixes GiovineItalia#1293

src/guide.jl

@@ -556,14 +556,15 @@ struct XTicks <: Gadfly.GuideElement
     end
 end
 
+XTicks(label, ticks::AbstractRange, orientation) = XTicks(label, collect(ticks), orientation)
 XTicks(; label=true, ticks=:auto, orientation=:auto) = XTicks(label, ticks, orientation)
 
 """
     Guide.xticks[(; label=true, ticks=:auto, orientation=:auto)]
     Guide.xticks(label, ticks, orientation)
 
 Formats the tick marks and labels for the x-axis.  `label` toggles the label
-visibility.  `ticks` can also be an array of locations, or `nothing`.
+visibility.  `ticks` can also be an array of locations, a range, or `nothing`.
 `orientation` can also be `:horizontal` or `:vertical`.
 """
 const xticks = XTicks
@@ -727,14 +728,15 @@ struct YTicks <: Gadfly.GuideElement
     end
 end
 
+YTicks(label, ticks::AbstractRange, orientation) = YTicks(label, collect(ticks), orientation)
 YTicks(; label=true, ticks=:auto, orientation=:horizontal) = YTicks(label, ticks, orientation)
 
 """
     Guide.yticks[(; label=true, ticks=:auto, orientation=:horizontal)]
     Guide.yticks(ticks, label, orientation)
 
 Formats the tick marks and labels for the y-axis.  `label` toggles the label
-visibility.  `ticks` can also be an array of locations, or `nothing`.
+visibility.  `ticks` can also be an array of locations, a range, or `nothing`.
 `orientation` can also be `:auto` or `:vertical`.
 """
 const yticks = YTicks

test/testscripts/explicit_xy_ticks_range.jl

@@ -0,0 +1,8 @@
+using Gadfly
+
+set_default_plot_size(6inch, 3inch)
+
+plot(x=[0.236033, 0.346517, 0.312707, 0.00790928, 0.488613, 0.210968, 0.951916, 0.999905, 0.251662, 0.986666],
+     y=[0.555751, 0.437108, 0.424718, 0.773223, 0.28119, 0.209472, 0.251379, 0.0203749, 0.287702, 0.859512],
+     Guide.xticks(ticks=0:1),
+     Guide.yticks(ticks=0.4:0.1:0.6))