Handle encoding uniformly

[dometto]

As per #19, we need to think about a way to handle the following encoding statements uniformly:

$ grep -r "force_encoding" lib/
lib//rugged_adapter/git_layer_rugged.rb:          files << [patch.delta.new_file[:path].force_encoding("UTF-8"), new_deletions, new_additions, patch.changes] # Rugged seems to generate the stat diffs in the other direciton than grit does by default, so switch the order of additions and deletions.
lib//rugged_adapter/git_layer_rugged.rb:            next unless line.force_encoding("UTF-8").match(/#{Regexp.escape(query)}/i)
lib//rugged_adapter/git_layer_rugged.rb:        patches.map  {|patch| OpenStruct.new(:diff => patch.to_s.split("\n")[2..-1].join("\n").force_encoding("UTF-8"))}.reverse # First remove two superfluous lines. Rugged seems to order the diffs differently than Grit, so reverse.