Use clone instead of creating new objects

While `clone` is supposed to create shallow copy, it seems it creates
clone for the delegator just fine. This results in simpler and more
readable code and most importantly, it will enable custom fields in
RpmDependency class.

Author: voxik

lib/gem2rpm/rpm_dependency.rb

@@ -12,31 +12,28 @@ def initialize(dependency)
 
     # Convert to rubygem() virtual provide dependency.
     def virtualize
-      dep = __getobj__.dup
-      dep.name = "rubygem(#{dep.name})"
-
-      self.class.new dep
+      clone.tap do |dep|
+        dep.name = "rubygem(#{dep.name})"
+      end
     end
 
     # Output dependency with RPM requires tag.
     def with_requires
-      dep = __getobj__.dup
-      dep.name = case dep.type
-      when :development
-        "BuildRequires: #{dep.name}"
-      else
-        "Requires: #{dep.name}"
+      clone.tap do |dep|
+        dep.name = case dep.type
+        when :development
+          "BuildRequires: #{dep.name}"
+        else
+          "Requires: #{dep.name}"
+        end
       end
-
-      self.class.new dep
     end
 
     # Comment out the dependency.
     def comment_out
-      dep = __getobj__.dup
-      dep.name = "# #{dep.name}"
-
-      self.class.new dep
+      clone.tap do |dep|
+        dep.name = "# #{dep.name}"
+      end
     end
 
     # Returns string with entry suitable for RPM .spec file.