add tox test environment for sqlite, and include elasticsearch

runtests.py

@@ -31,7 +31,7 @@ if not settings.configured:
     settings.configure(
         DATABASES={
             'default': {
-                'ENGINE': 'django.db.backends.postgresql_psycopg2',
+                'ENGINE': os.environ.get('DATABASE_ENGINE', 'django.db.backends.postgresql_psycopg2'),
                 'NAME': 'wagtaildemo',
                 'USER': 'postgres',
             }

tox.ini

@@ -1,6 +1,7 @@
 [tox]
 envlist =
-    py27-dj16-postgres
+    py27-dj16-postgres,
+    py27-dj16-sqlite
 
 [testenv]
 commands=./runtests.py
@@ -10,3 +11,16 @@ basepython=python2.7
 deps =
     Django>=1.6,<1.7
     psycopg2==2.5.2
+    pyelasticsearch==0.6.1
+    elasticutils==0.8.2
+setenv =
+    DATABASE_ENGINE=django.db.backends.postgresql_psycopg2
+
+[testenv:py27-dj16-sqlite]
+basepython=python2.7
+deps =
+    Django>=1.6,<1.7
+    pyelasticsearch==0.6.1
+    elasticutils==0.8.2
+setenv =
+    DATABASE_ENGINE=django.db.backends.sqlite3