remove the dependency on gcc-5

.travis.yml

@@ -10,16 +10,11 @@ addons:
     packages:
       - libblas-dev
       - liblapack-dev
+      - gcc
       - gfortran
 install:
   # We do this conditionally because it saves us some downloading if the
   # version is the same.
-  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
-  - sudo apt-get -qq update
-  - sudo apt-get -qq install g++-5
-  - sudo apt-get -qq install gcc-5
-  # - export CXX="g++-6" CC="gcc-6"
-  - sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 60 --slave /usr/bin/g++ g++ /usr/bin/g++-5
   - wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh
   - bash miniconda.sh -b -p $HOME/miniconda
   - export PATH="$HOME/miniconda/bin:$PATH"