Disable BUILD_WHEEL until we know it works, re #181

.travis.yml

@@ -31,7 +31,5 @@
     python: '3.6'
   - os: linux
     dist: xenial
-    sudo: required
-    services:
-      - docker
+    sudo: false
     python: '3.7'
@@ -37,5 +35,5 @@
     python: '3.7'
-    env: BUILD_SDIST=true BUILD_WHEEL=true
+    env: BUILD_SDIST=true
   - os: linux
     sudo: false
     python: pypy