added syntax sugar to check if URI is absolute or relative

spec/std/uri_spec.cr

@@ -54,6 +54,18 @@ describe "URI" do
     end
   end
 
+  describe "#absolute?" do
+    it { URI.parse("http://www.example.com/foo").absolute?.should eq(true) }
+    it { URI.parse("http://www.example.com").absolute?.should eq(true) }
+    it { URI.parse("file://").absolute?.should eq(true) }
+    it { URI.parse("foo").absolute?.should eq(false) }
+    it { URI.parse("foo").absolute?.should eq(false) }
+  end
+
+  describe "#relative?" do
+    it { URI.parse("/foo").relative?.should eq(true) }
+  end
+
   describe "normalize" do
     it "removes dot notation from path" do
       cases = {

src/uri.cr

@@ -144,6 +144,16 @@ class URI
     end
   end
 
+  # Returns `true` if URI has a *scheme* specified.
+  def absolute?
+    @scheme ? true : false
+  end
+
+  # Returns `true` if URI does not have a *scheme* specified.
+  def relative?
+    !absolute?
+  end
+
   def to_s(io : IO)
     if scheme
       io << scheme