Add python 3.7 to the Travis testing matrix (kensho-technologies#148)

* Add Python 3.7 target for TravisCI.

* No need for xenial target when everything is xenial.

* Advertise py3.7 compatibility in classifiers.

* Remove sudo=true option.

Author: obi1kenobi

.travis.yml

@@ -28,6 +28,10 @@ matrix:
     python: "3.6"
     script:
       - py.test --cov=graphql_compiler graphql_compiler/tests
+  - name: "Python 3.7 unit tests"
+    python: "3.7"
+    script:
+      - py.test --cov=graphql_compiler graphql_compiler/tests
 after_success:
   - docker-compose down
   - coveralls

setup.py

@@ -75,6 +75,7 @@ def find_long_description():
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
     ],
     keywords='graphql database compiler orientdb',
     python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*',