Drop Python 3.4 support

Some of the newer versions of our dependencies dropped support for
Python 3.4.

Python 3.4 has reached end of life and according to
https://en.wikipedia.org/wiki/CPython#Enterprise_Linux only Debian 8
shipped Python 3.4 to begin with.

.travis.yml

@@ -1,7 +1,6 @@
 language: python
 cache: pip
 python:
-    - 3.4
     - 3.5
     - 3.6
     - pypy3

README.rst

@@ -50,15 +50,15 @@ To update, run::
 
      $ pip install -U crash
 
-If you are not using Python version 3.4 or above, recent version of `pip`_ will
-only install version 0.23.x. This is because newer versions of this package are
-not compatible with Python 2.7 or 3.3 and below.
+If you are not using Python version 3.5 or above, recent version of `pip`_ will
+install an earlier version of Crash. This is because newer versions of this
+package are not compatible with Python 2.7 or 3.4 and below.
 
 Standalone
 ----------
 
 Crash is also available as a standalone executable that includes all the
-necessary dependencies, and can be run as long as Python (>= 3.4) is available
+necessary dependencies, and can be run as long as Python (>= 3.5) is available
 on your system.
 
 First, download the executable file::

setup.py

@@ -77,7 +77,7 @@ def read(path):
         ],
         argcompletion=['argcomplete']
     ),
-    python_requires='>=3.4',
+    python_requires='>=3.5',
     install_requires=requirements,
     package_data={'': ['*.txt']},
     classifiers=[
@@ -87,9 +87,9 @@ def read(path):
         'Operating System :: OS Independent',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy',
         'Topic :: Database'

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = pypy3, py34, py35, py36
+envlist = pypy3, py35, py36, py37
 
 [testenv]
 usedevelop = True