Drop Python 3.3 Support

It's reached end-of-life, and our dependencies have started to drop it.
See https://github.com/nvbn/thefuck/pull/744#issuecomment-353244371

.travis.yml

@@ -11,9 +11,6 @@ matrix:
     - os: linux
       dist: trusty
       python: "3.4"
-    - os: linux
-      dist: trusty
-      python: "3.3"
     - os: linux
       dist: trusty
       python: "2.7"

README.md

@@ -92,7 +92,7 @@ Reading package lists... Done
 
 ## Requirements
 
-- python (3.3+)
+- python (3.4+)
 - pip
 - python-dev
 

setup.py

@@ -26,8 +26,8 @@ if version < (2, 7):
     print('thefuck requires Python version 2.7 or later' +
           ' ({}.{} detected).'.format(*version))
     sys.exit(-1)
-elif (3, 0) < version < (3, 3):
-    print('thefuck requires Python version 3.3 or later' +
+elif (3, 0) < version < (3, 4):
+    print('thefuck requires Python version 3.4 or later' +
           ' ({}.{} detected).'.format(*version))
     sys.exit(-1)