Drop support for Python 3.3.

Fix oasis-open#52.

README.rst

@@ -22,15 +22,15 @@ documentation and to verify patterns express the desired criteria.
 Requirements
 ------------
 
--  Python 2.7.6+
+-  Python 2.7 or 3.4+
 -  ANTLR Python Runtime (4.7+)
 
    -  https://pypi.python.org/pypi/antlr4-python2-runtime (Python 2)
    -  https://pypi.python.org/pypi/antlr4-python3-runtime (Python 3)
 
 -  typing
 
-   -  https://pypi.python.org/pypi/typing (Python 3.0-3.4)
+   -  https://pypi.python.org/pypi/typing (Python 3.4)
 
 -  python-dateutil (https://dateutil.readthedocs.io/en/stable/)
 -  six (https://six.readthedocs.io/)
@@ -206,4 +206,3 @@ to [email protected].
    :target: https://travis-ci.org/oasis-open/cti-pattern-matcher
 .. |Coverage| image:: https://codecov.io/gh/oasis-open/cti-pattern-matcher/branch/master/graph/badge.svg
    :target: https://codecov.io/gh/oasis-open/cti-pattern-matcher
-

setup.py

@@ -8,7 +8,6 @@
     install_requires=[
         'antlr4-python2-runtime==4.7 ; python_version < "3"',
         'antlr4-python3-runtime==4.7 ; python_version >= "3"',
-        'enum34 ; python_version ~= "3.3.0"',
         'python-dateutil',
         'six',
         'stix2-patterns>=0.6.0',
@@ -28,7 +27,6 @@
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py33,py34,py35,py36,pycodestyle,isort-check
+envlist = py27,py34,py35,py36,style,isort-check
 
 [testenv]
 deps =
@@ -13,12 +13,10 @@ commands =
 
 passenv = CI TRAVIS TRAVIS_*
 
-[testenv:pycodestyle]
+[testenv:style]
 deps =
-  pycodestyle
   flake8
 commands =
-  pycodestyle ./stix2matcher
   flake8
 
 [testenv:isort-check]
@@ -37,7 +35,6 @@ max-line-length=160
 [travis]
 python =
   2.7: py27, pycodestyle
-  3.3: py33, pycodestyle
   3.4: py34, pycodestyle
   3.5: py35, pycodestyle
   3.6: py36, pycodestyle