message: Update travis config for stable.
diff: @@ -6,7 +6,6 @@ cache: cargo
  rust:
  - stable
  - - nightly
  os:
  - linux
  @@ -21,20 +20,37 @@ matrix:
  include:
  - os: linux
  env: GNUPLOT=no
  + - os: linux
  + env: GNUPLOT=no
  + rust: nightly
  + - os: linux
  + env: GNUPLOT=yes
  + addons:
  + apt:
  + packages:
  + - gnuplot
  - os: linux
  env: GNUPLOT=yes
  + rust: nightly
  addons:
  apt:
  packages:
  - gnuplot
  - os: linux
  env: CLIPPY=yes
  + rust: nightly
  - os: linux
  env: DOCS=yes
  - os: osx
  env: GNUPLOT=no
  - os: osx
  env: GNUPLOT=yes
  + - os: osx
  + env: GNUPLOT=no
  + rust: nightly
  + - os: osx
  + env: GNUPLOT=yes
  + rust: nightly
  before_script:
  - if [ "$DOCS" = "yes" ]; then
  