Add basic support for symbolic links.

test/test_file.rb

@@ -21,6 +21,20 @@ context "File" do
     assert_equal commit.author.name, file.version.author.name
   end
 
+  test "symbolic link" do
+    commit = @wiki.repo.commits.first
+    file   = @wiki.file("Data-Two.csv")
+
+    # Since we don't have a checkout here (bare repos in testing), these
+    # symbolic links won't resolve.  Stub IO.read to simulate the behavior
+    # and make sure all is working well.
+    path_to_link = File.expand_path(File.join('..', '..', 'Data.csv'), __FILE__)
+    File.expects(:file?).with(path_to_link).returns(true)
+    IO.expects(:read).with(path_to_link).returns('symlink test')
+
+    assert_equal file.raw_data, 'symlink test'
+  end
+
   test "accessing tree" do
     assert_nil @wiki.file("Mordor")
   end