Test by default against Django 1.7

Signed-off-by: Michal Čihař <michal@cihar.com>

.travis.yml

@@ -3,17 +3,16 @@ python:
   - "2.7"
 # - Test against all supported Django versions with sqlite
 # - Test against all supported databases with current Django
-# - Test against RC version of Django
 # - Run Selenium tests on current Django
 # - Run pylint/pep8 checker
 env:
   matrix:
-    - DJANGO_PIP="Django>=1.6,<1.7" DO_LINT=1
-    - DJANGO_PIP="Django>=1.6,<1.7" TRAVIS_DATABASE=mysql
-    - DJANGO_PIP="Django>=1.6,<1.7" TRAVIS_DATABASE=postgresql
-    - DJANGO_PIP="Django>=1.6,<1.7"
+    - DJANGO_PIP="Django>=1.7,<1.8" DO_LINT=1
+    - DJANGO_PIP="Django>=1.7,<1.8" TRAVIS_DATABASE=mysql
+    - DJANGO_PIP="Django>=1.7,<1.8" TRAVIS_DATABASE=postgresql
     - DJANGO_PIP="Django>=1.7,<1.8"
-    - DJANGO_PIP="Django>=1.6,<1.7" TRAVIS_DATABASE=mysql TRAVIS_RUN_TESTS="-p test_selenium.py" DO_SELENIUM=1
+    - DJANGO_PIP="Django>=1.6,<1.7"
+    - DJANGO_PIP="Django>=1.7,<1.8" TRAVIS_DATABASE=mysql TRAVIS_RUN_TESTS="-p test_selenium.py" DO_SELENIUM=1
 before_install:
   - git clone --depth 1 --branch v0.1.2 https://github.com/ruleant/buildtime-trend.git $HOME/buildtime-trend 
   - source $HOME/buildtime-trend/init.sh