Drop support for end-of-lifed Python versions

The following versions of Python are no longer supported by the core
developers of Python and pip:

- Python 2.6
    - End of life on 2013-10-29 [1]
    - Dropped from pip on 2017-03-18 [2]
- Python 3.3
    - End of life on 2017-09-29 [3]
    - Dropped from pip on 2017-03-22 [4]

Developers should migrate off of these versions ASAP, as they may be
missing critical security fixes.

[1] https://www.python.org/dev/peps/pep-0361/#release-lifespan
[2] pypa/pip#4343
[3] https://www.python.org/dev/peps/pep-0398/#lifespan
[4] pypa/pip#4355

.travis.yml

@@ -5,9 +5,7 @@ language: python
 python:
   - "3.5"
   - "3.4"
-  - "3.3"
   - "2.7"
-  - "2.6"
   - "pypy"
 
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors

CONTRIBUTING.rst

@@ -99,7 +99,7 @@ Before you submit a pull request, check that it meets these guidelines:
 2. If the pull request adds functionality, the docs should be updated. Put
    your new functionality into a function with a docstring, and add the
    feature to the list in README.rst.
-3. The pull request should work for Python 2.6, 2.7, 3.3, and 3.4, 3.5, and for PyPy. Check
+3. The pull request should work for Python 2.7, and 3.4, 3.5, and for PyPy. Check
    https://travis-ci.org/bndr/pipreqs/pull_requests
    and make sure that the tests pass for all supported Python versions.
 

setup.py

@@ -45,10 +45,8 @@
         'License :: OSI Approved :: Apache Software License',
         'Natural Language :: English',
         "Programming Language :: Python :: 2",
-        'Programming Language :: Python :: 2.6',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
     ],

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py26, py27, py33, py34, py35
+envlist = py27, py34, py35
 
 [testenv]
 setenv =