Fix #44

The problem here was the precedence of `or` vs `||`. Switching to `||` resulted
in the expected behaviour.

lib/diff/lcs/ldiff.rb

@@ -105,7 +105,7 @@ def run(args, _input = $stdin, output = $stdout, error = $stderr) #:nodoc:
     if @binary.nil?
       old_txt = data_old[0, 4096].scan(/\0/).empty?
       new_txt = data_new[0, 4096].scan(/\0/).empty?
-      @binary = !old_txt or !new_txt
+      @binary = !old_txt || !new_txt
     end
 
     unless @binary