Update .travis.yml

.travis.yml

@@ -4,17 +4,16 @@ sudo: false
 # Python versions for matrix
 language: python
 python:
-  - "3.3"
   - "3.4"
   - "3.5"
   - "3.6"
+  - "3.7"
 
 # Django versions for matrix
 env:
   - DJANGO_VERSION='>=1.10,<1.11'
   - DJANGO_VERSION='>=1.11,<1.12'
   - DJANGO_VERSION='>=2.0,<2.1'
-  - DJANGO_VERSION='>=2.1,<2.2'
 
 # Command to install dependencies, e.g. pip install -r requirements.txt
 install: