future/builtins/misc.py doesn't use absolute import

[d-b-w]

This can cause a failure when there is a file called io.py in the same directory as a script.

Given two one line files:
script_under_test.py : import builtins
io.py : raise AssertionError("Don't import me")

python script_under_test.py

causes the following error:

  File "./bug_report/script_under_test.py", line 1, in <module>
    import builtins
  File "VE/lib/python2.7/site-packages/builtins/__init__.py", line 8, in <module>
    from future.builtins import *
  File "VE/lib/python2.7/site-packages/future/builtins/__init__.py", line 13, in <module>
    from future.builtins.misc import (ascii, chr, hex, input, isinstance, next,
  File "VE/lib/python2.7/site-packages/future/builtins/misc.py", line 43, in <module>
    from io import open
  File "/scr/dbw/hackNtest/bug_report/io.py", line 1, in <module>
    raise AssertionError("Don't import me")
  AssertionError: Don't import me```