support 2.7, remove support for 2.6 3.3 pypy

.travis.yml

@@ -1,11 +1,8 @@
 language: python
 python:
-  - "2.6"
   - "2.7"
-  - "3.3"
   - "3.4"
   - "3.5"
-  - "pypy"
 
 notifications:
   email:

click_spinner/__init__.py

@@ -1,5 +1,3 @@
-from builtins import next
-from builtins import object
 import sys
 import threading
 import time