Add 3.7 to to travis config

.travis.yml

@@ -5,12 +5,14 @@ python:
   - 3.4
   - 3.5
   - 3.6
+  - 3.7
 
 env:
   - JEDI_TEST_ENVIRONMENT=27
   - JEDI_TEST_ENVIRONMENT=34
   - JEDI_TEST_ENVIRONMENT=35
   - JEDI_TEST_ENVIRONMENT=36
+  - JEDI_TEST_ENVIRONMENT=37
 
 addons:
   apt:
@@ -22,7 +24,6 @@ matrix:
   allow_failures:
     - python: pypy
     - env: TOXENV=sith
-    - python: 3.7-dev
   include:
     - python: 3.6
       env:
@@ -33,7 +34,7 @@ matrix:
     # For now ignore pypy, there are so many issues that we don't really need
     # to run it.
     #- python: pypy
-    - python: "3.7-dev"
+    - python: "nightly"
 before_install:
     - ./travis_install.sh
     # Need to add the path to the Python versions in the end. This might add