tests: run npm install before running tests

Author: asfaltboy

tox.ini

@@ -3,6 +3,7 @@ envlist =
   {py27,pypy,py34}-django{111}
   py35-django{20,22,111,-master}
   py36-django{111,22,-master}
+  py37-django{111,22,-master}
   docs
 
 [testenv]
@@ -29,6 +30,7 @@ setenv =
     DJANGO_SETTINGS_MODULE = tests.settings
     PYTHONPATH = {toxinidir}
 commands =
+    npm install
     {envbindir}/coverage run --source pipeline {envbindir}/django-admin.py test {posargs:tests}
     {envbindir}/coverage report