Fix compatibility with Python 2.5.

Emulate next(b, None) through  for loop with single round.
There wasn't print_function, while it really doesn't needed.

jsonpointer.py

@@ -217,5 +217,6 @@ class JsonPointer(object):
 def pairwise(iterable):
     "s -> (s0,s1), (s1,s2), (s2, s3), ..."
     a, b = tee(iterable)
-    next(b, None)
+    for _ in b:
+        break
     return izip(a, b)

tests.py

@@ -1,7 +1,6 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-from __future__ import print_function
 import doctest
 import unittest
 import sys
@@ -73,7 +72,8 @@ if coverage is not None:
     coverage.erase()
 
 if coverage is None:
-    print("""
-    No coverage reporting done (Python module "coverage" is missing)
-    Please install the python-coverage package to get coverage reporting.
-    """, file=sys.stderr)
+    sys.stderr.write("""
+No coverage reporting done (Python module "coverage" is missing)
+Please install the python-coverage package to get coverage reporting.
+""")
+    sys.stderr.flush()