Revert "Drop support of CPython 3.4"

This reverts commit 5e3654757d.

.travis.yml

@@ -2,6 +2,7 @@ language: python
 sudo: false
 python:
   - 2.7
+  - 3.4
   - 3.5
   - 3.7-dev
   - pypy

README.rst

@@ -107,8 +107,8 @@ Release history:
 1. Download & installation
 --------------------------
 
-Mpmath requires Python 2.7 or 3.5 (or later versions). It has been tested
-with CPython 2.7, 3.5 through 3.7 and for PyPy.
+Mpmath requires Python 2.7 or 3.4 (or later versions). It has been tested
+with CPython 2.7, 3.4 through 3.7 and for PyPy.
 
 The latest release of mpmath can be downloaded from the mpmath
 website and from https://github.com/fredrik-johansson/mpmath/releases

setup.cfg

@@ -13,6 +13,7 @@ classifiers = License :: OSI Approved :: BSD License
               Programming Language :: Python :: 2
               Programming Language :: Python :: 2.7
               Programming Language :: Python :: 3
+              Programming Language :: Python :: 3.4
               Programming Language :: Python :: 3.5
               Programming Language :: Python :: 3.6
               Programming Language :: Python :: 3.7