Clean up travis configuration

Author: macro1

.travis.yml

@@ -7,26 +7,25 @@ python:
   - 3.3
 
 env:
-  - DJANGO=Django==1.4.13
-  - DJANGO=Django==1.5.8
-  - DJANGO=Django==1.6.5
+  - DJANGO="Django>=1.4,<1.5"
+  - DJANGO="Django>=1.6,<1.7"
   - DJANGO="Django>=1.7,<1.8"
 
 install:
-  - pip install coverage coveralls $DJANGO --use-mirrors
+  - pip install -U coverage coveralls $DJANGO
 
 script: coverage run -a setup.py test
 
 matrix:
   exclude:
    - python: 2.6
-     env: DJANGO=Django==1.6.5
+     env: DJANGO="Django>=1.6,<1.7"
    - python: 2.6
      env: DJANGO="Django>=1.7,<1.8"
    - python: 3.2
-     env: DJANGO=Django==1.4.13
+     env: DJANGO="Django>=1.4,<1.5"
    - python: 3.3
-     env: DJANGO=Django==1.4.13
+     env: DJANGO="Django>=1.4,<1.5"
 
   include:
    - python: 3.4