triangle: Add tests for floats

These have always been present, ever since
exercism/problem-specifications#424. If the
Crystal track wishes its generator to produce the test suite, without
need for post-hoc modification of the generated output, then it seems
the two choices are:

1. Include the cases
2. Add code that detects float inputs and does not output those cases.

This commit implements the former plan.

exercises/triangle/spec/triangle_spec.cr

@@ -18,6 +18,10 @@ describe "Triangle" do
     Triangle.new([0, 0, 0]).equilateral?.should eq(false)
   end
 
+  pending "sides may be floats" do
+    Triangle.new([0.5, 0.5, 0.5]).equilateral?.should eq(true)
+  end
+
   pending "true if last two sides are equal" do
     Triangle.new([3, 4, 4]).isosceles?.should eq(true)
   end
@@ -42,6 +46,10 @@ describe "Triangle" do
     Triangle.new([1, 1, 3]).isosceles?.should eq(false)
   end
 
+  pending "sides may be floats" do
+    Triangle.new([0.5, 0.4, 0.5]).isosceles?.should eq(true)
+  end
+
   pending "true if no sides are equal" do
     Triangle.new([5, 4, 6]).scalene?.should eq(true)
   end
@@ -57,4 +65,8 @@ describe "Triangle" do
   pending "Sides that violate triangle inequality are not scalene, even if they are all different" do
     Triangle.new([7, 3, 2]).scalene?.should eq(false)
   end
+
+  pending "sides may be floats" do
+    Triangle.new([0.5, 0.4, 0.6]).scalene?.should eq(true)
+  end
 end

exercises/triangle/src/example.cr

@@ -1,5 +1,5 @@
 class Triangle
-  def initialize(sides)
+  def initialize(sides : Array(Int32) | Array(Float64))
     @sides = sides
     @sides = [] of Int32 if illegal?
   end