Merge pull request #1664 from rcurtin/travis-xenial

Try to use xenial since it is stable.

.travis.yml

@@ -1,5 +1,5 @@
 sudo: required
-dist: trusty
+dist: xenial
 language: cpp
 
 env:
@@ -8,18 +8,10 @@ env:
   - CMAKE_OPTIONS="-DDEBUG=ON -DPROFILE=OFF -DBUILD_PYTHON_BINDINGS=OFF"
 
 before_install:
-  # For the python bindings we need cython >= 0.24.
-  - sudo add-apt-repository -y ppa:imcode/s3ql-trusty-backport
-  # For the python bindings we need pandas >= 0.15.0.
-  - wget -O- http://neuro.debian.net/lists/trusty.us-ca.full | sudo tee /etc/apt/sources.list.d/neurodebian.sources.list
-  - sudo apt-key adv --recv-keys --keyserver hkp://ha.pool.sks-keyservers.net 0xA5D32F012649A5A9 ||
-    sudo apt-key adv --recv-keys --keyserver hkp://pgp.mit.edu 0xA5D32F012649A5A9 ||
-    sudo apt-key adv --recv-keys --keyserver hkp://keyserver.pgp.com 0xA5D32F012649A5A9
   - sudo apt-get update
   - sudo apt-get install -y --allow-unauthenticated libopenblas-dev liblapack-dev g++ libboost-all-dev python3-pip cython3 python3-numpy python3-pandas
   # Install both python2 and python3 modules, and the build will decide which to
   # use.
-  - sudo pip install cython numpy pandas
   - sudo pip install --upgrade --ignore-installed setuptools
   - sudo pip3 install --upgrade --ignore-installed setuptools
   - curl https://ftp.fau.de/macports/distfiles/armadillo/armadillo-6.500.5.tar.gz | tar xvz && cd armadillo*