Drop testing for EOL Pythons 3.2 & 3.3 (#271)

Python 3.2 and 3.3 are end of life. They are no longer receiving bug
fixes, including for security issues. Python 3.3 went EOL on 2017-09-29
and Python 3.2 on 2016-02-20. For additional details on supported Python
versions, see:

https://devguide.python.org/#status-of-python-branches

Removing support for EOL Pythons will reduce necessary testing and
maintenance resources.

Pass python_requires argument to setuptools to help pip decide what
version of the library to install.

Using pypinfo, here are the download statistics for the last 30 days,
showing very minimal use of these EOL pythons:

$ pypinfo --percent pycparser pyversion

| python_version | percent | download_count |
| -------------- | ------- | -------------- |
| 2.7            |  71.64% |      1,373,309 |
| 3.6            |  15.78% |        302,407 |
| 3.5            |   8.32% |        159,452 |
| 3.4            |   3.80% |         72,850 |
| 2.6            |   0.32% |          6,187 |
| 3.7            |   0.12% |          2,263 |
| 3.3            |   0.02% |            360 |
| 3.2            |   0.00% |             15 |
| 3.8            |   0.00% |              5 |
| None           |   0.00% |              1 |

1 files changed, 1 insertions, 1 deletions

diff --git a/README.rst b/README.rst
index b8d9f17..4af8160 100644
--- a/README.rst
+++ b/README.rst
@@ -79,7 +79,7 @@ Installing
 Prerequisites
 -------------
 
-* **pycparser** was tested on Python 2.7, 3.3-3.6, on both Linux and
+* **pycparser** was tested on Python 2.7, 3.4-3.6, on both Linux and
   Windows. It should work on any later version (in both the 2.x and 3.x lines)
   as well.