Allow be matcher to be used on structs

spec/rspec/core/explicit_subject_spec.cr

@@ -115,11 +115,11 @@ Spectator.describe "Explicit Subject" do
       end
 
       it "the subject and named helpers return the same object" do
-        expect(global_count).to eq(subject) # TODO: `be` matcher with value (no same? method).
+        expect(global_count).to be(subject)
       end
 
       it "is set to the block return value (i.e. the global $count)" do
-        expect(global_count).to eq(@@count) # TODO: `be` matcher with value (no same? method).
+        expect(global_count).to be(@@count)
       end
     end
   end

spec/rspec/core/helper_methods_spec.cr

@@ -8,7 +8,7 @@ Spectator.describe "Arbitrary helper methods" do
       end
 
       it "has access to methods define in its group" do
-        expect(help).to eq(:available) # TODO: `be` matcher with value (no same? method).
+        expect(help).to be(:available)
       end
     end
   end
@@ -21,7 +21,7 @@ Spectator.describe "Arbitrary helper methods" do
 
       describe "in a nested group" do
         it "has access to methods defined in its parent group" do
-          expect(help).to eq(:available) # TODO: `be` matcher with value (no same? method).
+          expect(help).to be(:available)
         end
       end
     end

src/spectator/matchers/reference_matcher.cr

@@ -13,7 +13,13 @@ module Spectator::Matchers
 
     # Checks whether the matcher is satisifed with the expression given to it.
     private def match?(actual : TestExpression(T)) : Bool forall T
-      expected.value.same?(actual.value)
+      value = expected.value
+      if value.responds_to?(:same)
+        value.same?(actual.value)
+      else
+        # Value type (struct) comparison.
+        actual.value.class == value.class && actual.value == value
+      end
     end
 
     # Message displayed when the matcher isn't satisifed.