travis fix

Author: vdboor

.travis.yml

@@ -5,25 +5,26 @@ python:
 - '3.3'
 - '3.4'
 env:
-- DJANGO="django>=1.5.0,<1.6.0 django-mptt<0.7.0"
-- DJANGO="django>=1.6.0,<1.7.0 django-mptt<0.8.0"
-- DJANGO="django>=1.7.0,<1.8.0 django-mptt<0.8.0
-- DJANGO="django>=1.8.0,<1.9.0"
-- DJANGO="django>=1.9.0,<1.10.0"
+- PACKAGES="django>=1.5.0,<1.6.0 django-mptt<0.7.0"
+- PACKAGES="django>=1.6.0,<1.7.0 django-mptt<0.8.0"
+- PACKAGES="django>=1.7.0,<1.8.0 django-mptt<0.8.0
+- PACKAGES="django>=1.8.0,<1.9.0"
+- PACKAGES="django>=1.9.0,<1.10.0"
 matrix:
   exclude:
   - python: '2.6'
-    env: DJANGO="django>=1.7.0,<1.8.0 django-mptt<0.8.0"
+    env: PACKAGES="django>=1.7.0,<1.8.0 django-mptt<0.8.0"
   - python: '2.6'
-    env: DJANGO="django>=1.8.0,<1.9.0"
+    env: PACKAGES="django>=1.8.0,<1.9.0"
   - python: '2.6'
-    env: DJANGO="django>=1.9.0,<1.10.0"
+    env: PACKAGES="django>=1.9.0,<1.10.0"
   - python: '3.3'
-    env: DJANGO="django>=1.9.0,<1.10.0"
+    env: PACKAGES="django>=1.9.0,<1.10.0"
 before_install:
 - pip install codecov
 install:
-- travis_retry pip install $DJANGO
+- pip install -U pip wheel
+- pip install $PACKAGES
 - pip install -e .
 script:
 - coverage run --source=polymorphic_tree runtests.py