Generate coverage (python#22)

Author: brettcannon

.travis.yml

@@ -1,15 +1,20 @@
 language: python
 cache: pip
-python:
-  - "3.4"
-  - "3.5-dev"
-  - "3.6-dev"
+matrix:
+  include:
+    - python: "3.4"
+      env: GEVER=35
+    - python: "3.5-dev"
+      env: GEVER=36
+    - python: "3.6-dev"
+      env: GEVER=37 LEVER=35
+    - python: "3.7-dev"
 
 install:
-  - python3 -m pip install --upgrade mypy
+  - python3 -m pip install --upgrade mypy coverage
 
 script:
-  - python3 -m unittest discover
+  - python3 -m coverage run -m unittest discover
   - mypy --ignore-missing-imports importlib_resources
 
 after_success: