tox: Add python 3.7 to build matrix

Signed-off-by: Rhys Kidd <rhyskidd@gmail.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

.travis.yml

@@ -21,6 +21,9 @@ matrix:
       env: TOX_ENV="py35-{generator,noaccel,accel-nix,streams}"
     - python: 3.6
       env: TOX_ENV="py36-{generator,noaccel,accel-nix,streams}"
+    - python: 3.7
+      env: TOX_ENV="py37-{generator,noaccel,accel-nix,streams}"
+      dist: xenial    # required for Python 3.7 (travis-ci/travis-ci#9069)
     - env: BUILD=cmake
 
 install:

tox.ini

 [tox]
-envlist = py{27,34,35,36}-{generator,noaccel}, py{27,34,35,36}-accel-{win,nix}, py{27,34,35,36}-streams
+envlist = py{27,34,35,36,37}-{generator,noaccel}, py{27,34,35,36,37}-accel-{win,nix}, py{27,34,35,36,37}-streams
 skipsdist = True
 
 [pytest]
@@ -14,12 +14,13 @@ setenv =
 deps =
     accel-nix: lxml
     accel: simplejson
-    generator: numpy==1.7.0
+    py{27,34,35,36}-generator: numpy==1.7.0
+    py37-generator: numpy
     mock==1.0.1
-    py27-accel-nix,py{34,35,36}-{accel,noaccel}: psutil
+    py27-accel-nix,py{34,35,36,37}-{accel,noaccel}: psutil
     py27-accel-nix: backports.lzma
     py27-accel-nix: subprocess32
-    py{35,36}: mako==1.0.2
+    py{35,36,37}: mako==1.0.2
     pytest==3.2.5
     pytest-mock
     pytest-pythonpath