Merge remote-tracking branch 'origin/drop-py2.6'

* origin/drop-py2.6:
  Drop support for Python 2.6

.travis.yml

@@ -3,7 +3,6 @@
 
 language: python
 python:
-  - "2.6"
   - "2.7"
   - "3.3"
   - "3.4"

setup.py

@@ -1,4 +1,3 @@
-import sys
 import re
 import ast
 
@@ -17,10 +16,6 @@ with open('./README.rst') as f:
 
 
 install_requires = ["pip >= 6.0.0"]
-if sys.version_info < (2, 7):
-    install_requires.append('argparse')
-    install_requires.append('ordereddict')
-    install_requires.append('importlib')
 
 
 setup(
@@ -34,6 +29,7 @@ setup(
     long_description=long_desc,
     install_requires=install_requires,
     extras_require={'graphviz': ['graphviz']},
+    python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*',
     py_modules=['pipdeptree'],
     entry_points={
         'console_scripts': [
@@ -45,7 +41,6 @@ setup(
         'Intended Audience :: Developers',
         'License :: OSI Approved :: MIT License',
         'Programming Language :: Python',
-        'Programming Language :: Python :: 2.6',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.3',

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py26, py27, py33, py34, py35, py36
+envlist = py27, py33, py34, py35, py36
 
 [testenv]
 commands =