Revert "Python 3: file() --> open() in yaml-highlight example (#236)"

This reverts commit a5f4329.

Still not working with python3:
    % PYTHONPATH=$PWD/lib3 python3 examples/yaml-highlight/yaml_hl.py <.appveyor.yml
    Traceback (most recent call last):
      File "examples/yaml-highlight/yaml_hl.py", line 126, in <module>
        hl.highlight()
      File "examples/yaml-highlight/yaml_hl.py", line 66, in highlight
        if input.startswith(codecs.BOM_UTF16_LE):
    TypeError: startswith first arg must be str or a tuple of str, not bytes

and getting this warning in python2:
Exception AttributeError: "'NoneType' object has no attribute 'stdin'" in <bound method YAMLHighlight.__del__ of <__main__.YAMLHighlight instance at 0x7fb9b81a47a0>> ignored

examples/yaml-highlight/yaml_hl.py

@@ -2,12 +2,6 @@
 
 import yaml, codecs, sys, os.path, optparse
 
-try:
-    unicode
-except NameError:
-    unicode = str
-
-
 class Style:
 
     def __init__(self, header=None, footer=None,
@@ -43,24 +37,17 @@ def __setstate__(self, state):
 class YAMLHighlight:
 
     def __init__(self, options):
-        with open(options.config, 'rb') as yaml_file:
-            config = yaml.load(yaml_file.read())
+        config = yaml.load(file(options.config, 'rb').read())
         self.style = config[options.style]
         if options.input:
-            self.input = open(options.input, 'rb')
+            self.input = file(options.input, 'rb')
         else:
             self.input = sys.stdin
         if options.output:
-            self.output = open(options.output, 'wb')
+            self.output = file(options.output, 'wb')
         else:
             self.output = sys.stdout
 
-    def __del__(self):
-        if self.input not in (sys.stdin, None):
-            self.input.close()
-        if self.output not in (sys.stdout, None):
-            self.output.close()
-
     def highlight(self):
         input = self.input.read()
         if input.startswith(codecs.BOM_UTF16_LE):