Skip specs that require gem unicode/emoji (optional dependency).

--- a/spec/display_width_spec.rb
+++ b/spec/display_width_spec.rb
@@ -148,15 +148,15 @@
   end
 
   describe '[emoji]' do
-    it 'does not count modifiers and zjw sequences for valid emoji' do
+    xit 'does not count modifiers and zjw sequences for valid emoji' do
       expect( "🤾🏽‍♀️".display_width(1, {}, emoji: true) ).to eq 2
     end
 
-    it 'respects different ambiguous values' do
+    xit 'respects different ambiguous values' do
       expect( "🤾🏽‍♀️".display_width(2, {}, emoji: true) ).to eq 2
     end
 
-    it 'works with flags' do
+    xit 'works with flags' do
       expect( "🇵🇹".display_width(1, {}, emoji: true) ).to eq 2
     end
   end
@@ -167,7 +167,7 @@
     Unicode::DisplayWidth.new(
       # ambiguous: 1,
       overwrite: { "A".ord => 100 },
-      emoji: true
+      emoji: false
     )
   end
 
@@ -175,7 +175,7 @@
     expect( display_width.of "A" ).to eq 100
   end
 
-  it "will respect given emoji option" do
+  xit "will respect given emoji option" do
     expect( display_width.of "🤾🏽‍♀️" ).to eq 2
   end
 end