Account for trailing newlines

*Backfills hunk_generator with extra newline to account for 'true'
trailing newlines that should be included in diff calculation.
  Example:

  "cat\n".split("\n") => []
  "cat\n\n".split("\n") => ["cat"]

  "cat\n".split("\n", -1) => ["cat", ""]
  "cat\n\n".split("\n", -1) => ["cat", "", ""]

*Removes extra newline representation from hunk_generator when crafting differ
output message.

lib/rspec/support/differ.rb

@@ -46,7 +46,10 @@ def diff_as_string(actual, expected)
           end
         end
 
-        finalize_output(output, hunks.last.diff(format_type).to_s) if hunks.last
+        if hunks.last
+          last_hunk_diff = hunks.last.diff(format_type).to_s.strip
+          finalize_output(output, last_hunk_diff)
+        end
 
         color_diff output
       rescue Encoding::CompatibilityError

lib/rspec/support/hunk_generator.rb

@@ -24,11 +24,11 @@ def diffs
       end
 
       def expected_lines
-        @expected.split("\n").map! { |e| e.chomp }
+        @expected.to_s.split("\n", -1).map! { |e| e.chomp }
       end
 
       def actual_lines
-        @actual.split("\n").map! { |e| e.chomp }
+        @actual.to_s.split("\n", -1).map! { |e| e.chomp }
       end
 
       def build_hunk(piece)