Revert "setup.py: add install_requires for future"

This reverts commit cd2dd96.

Author: wroberts

setup.py

@@ -30,7 +30,6 @@
       author_email     = 'wildwilhelm@gmail.com',
       url              = 'https://github.com/wroberts/pytimeparse',
       packages         = ['pytimeparse'],
-      install_requires = ['future'],
       license          = 'MIT',
       install_requires = INSTALL_REQUIRES,
       long_description = LONG_DESCRIPTION,