Remove pretty_format_json simplejson dependency

 * The simplejson module is only needed for <=py25 so replace with builtin json.
 * Replace six dependecy for simple Py2 check for convertion to unicode.
 * Cleanup quotes.
diff --git a/tests/pretty_format_json_test.py b/tests/pretty_format_json_test.py
index eeef65b..4054b4c 100644
--- a/tests/pretty_format_json_test.py
+++ b/tests/pretty_format_json_test.py
@@ -1,6 +1,7 @@
 import shutil
 
 import pytest
+from six import PY2
 
 from pre_commit_hooks.pretty_format_json import parse_indent
 from pre_commit_hooks.pretty_format_json import pretty_format_json
@@ -17,6 +18,7 @@
         parse_indent('-2')
 
 
+
 @pytest.mark.parametrize(
     ('filename', 'expected_retval'), (
         ('not_pretty_formatted_json.json', 1),
@@ -43,6 +45,7 @@
     assert ret == expected_retval
 
 
+@pytest.mark.skipif(PY2, reason="Requires Python3")
 @pytest.mark.parametrize(
     ('filename', 'expected_retval'), (
         ('not_pretty_formatted_json.json', 1),
@@ -52,7 +55,7 @@
         ('tab_pretty_formatted_json.json', 0),
     ),
 )
-def test_tab_pretty_format_json(filename, expected_retval):
+def test_tab_pretty_format_json(filename, expected_retval):  # pragma: no cover
     ret = pretty_format_json(['--indent', '\t', get_resource_path(filename)])
     assert ret == expected_retval