remove unused diff_engine class

lib/diff_engine.rb

@@ -1,25 +0,0 @@
-# This class is used to generate diffs, it will be consumed by the UI on the client that displays diffs.
-#
-# There are potential performance issues associated with diffing large amounts of completely
-# different text, see answer here for optimization if needed
-# http://meta.stackoverflow.com/questions/127497/suggested-edit-diff-shows-different-results-depending-upon-mode
-
-class DiffEngine
-
-  # Generate an html friendly diff
-  #
-  #  returns: html containing decorations indicating the changes
-  def self.html_diff(html_before, html_after)
-    # tokenize
-    # remove leading/trailing common
-    # SES
-    # format diff
-  end
-
-  # Same as html diff, except that it operates on markdown
-  #
-  # returns html containing decorated areas where diff happened
-  def self.markdown_diff(markdown_before, markdown_after)
-
-  end
-end