Move ES env vars to py36 job

Author: humitos

.travis.yml

@@ -1,10 +1,10 @@
 language: python
 python:
   - 3.6
-env:
-  - ES_VERSION=1.3.9 ES_DOWNLOAD_URL=https://download.elastic.co/elasticsearch/elasticsearch/elasticsearch-${ES_VERSION}.tar.gz
 matrix:
   include:
+    - python: 3.6
+      env: TOXENV=py36 ES_VERSION=1.3.9 ES_DOWNLOAD_URL=https://download.elastic.co/elasticsearch/elasticsearch/elasticsearch-${ES_VERSION}.tar.gz
     - python: 3.6
       env: TOXENV=docs
     - python: 3.6