Attempt to fix travis

Author: marcharper

.travis.yml

@@ -1,16 +1,13 @@
-
+dist: xenial
+services:
+  - xvfb
 language: python
 python:
   - 3.5
   - 3.6
-
 cache:
   directories:
     - $TRAVIS_BUILD_DIR/.hypothesis
-
-before_install:
-  - export DISPLAY=:99.0
-  - sh -e /etc/init.d/xvfb start
 install:
   - pip install -r requirements.txt
   - pip install sphinx

requirements.txt

@@ -1,5 +1,6 @@
 cloudpickle>=0.2.1
-dask>=0.18.1
+fsspec>=0.4.3
+dask>=2.3.0
 hypothesis==3.2
 matplotlib>=2.0.0
 numpy>=1.9.2