Make sure we're only dealing with UTF-8 when unencoding.

Closes #154.

lib/addressable/uri.rb

@@ -424,8 +424,13 @@ def self.unencode(uri, return_type=String, leave_encoded='')
           "Expected Class (String or Addressable::URI), " +
           "got #{return_type.inspect}"
       end
-      result = uri.gsub(/%[0-9a-f]{2}/i) do |sequence|
+      uri = uri.dup
+      # Seriously, only use UTF-8. I'm really not kidding!
+      uri.force_encoding("utf-8") if uri.respond_to?(:force_encoding)
+      leave_encoded.force_encoding("utf-8") if leave_encoded.respond_to?(:force_encoding)
+      result = uri.gsub(/%[0-9a-f]{2}/iu) do |sequence|
         c = sequence[1..3].to_i(16).chr
+        c.force_encoding("utf-8") if c.respond_to?(:force_encoding)
         leave_encoded.include?(c) ? sequence : c
       end
       result.force_encoding("utf-8") if result.respond_to?(:force_encoding)

spec/addressable/uri_spec.rb

@@ -5426,6 +5426,10 @@ def to_str
     Addressable::URI.unencode_component("g%C3%BCnther").should == "günther"
   end
 
+  it "should consistently use UTF-8 internally" do
+    Addressable::URI.unencode_component("ski=%BA%DAɫ").should == "ski=\xBA\xDAɫ"
+  end
+
   it "should result in correct percent encoded sequence as a URI" do
     Addressable::URI.unencode(
       "/path?g%C3%BCnther", ::Addressable::URI