Fixed CI build.

With Django 2.2 and above, GDAL 1.10 is no longer suppoted, and travis only supports GDAL 1.10 by default. Fixed tests to Django version 2.1.9 for now.

Author: yellowcap

.travis.yml

@@ -1,12 +1,9 @@
 language: python
 
 python:
-  - '3.4'
   - '3.5'
   - '3.6'
 
-sudo: true
-
 addons:
   postgresql: 9.6
   apt:
@@ -21,6 +18,7 @@ before_script:
   - psql -c 'create extension postgis' -U postgres -d raster_test
 
 install:
+  - pip install django==2.1.9
   - pip install -e .
   - pip install psycopg2-binary==2.7.7
   - pip install flake8==3.7.7