Remove tests for 1.7 and against pypy

Author: Emmanouil Konstantinidis

.travis.yml

@@ -2,20 +2,16 @@ language: python
 
 python:
   - "2.7"
-  - "3.3"
   - "3.4"
   - "3.5"
-  - "pypy"
-  - "pypy3"
 
 env:
-  - DJANGO_VERSION=1.7
   - DJANGO_VERSION=1.8
   - DJANGO_VERSION=1.9
 
 install:
   - pip install -r requirements.txt
-  - pip install -U django==$DJANGO_VERSION
+  - pip install -U Django==$DJANGO_VERSION
 
 script:
   - python runtests.py