message: Trying to speed up docs build.
diff: @@ -5,7 +5,8 @@ if [ "$CLIPPY" = "yes" ]; then
  fi
  if [ "$DOCS" = "yes" ]; then
  - cargo install mdbook mdbook-linkcheck --force
  + cargo install mdbook --no-default-features --force
  + cargo install mdbook-linkcheck --force
  fi
  if [ "$TRAVIS_OS_NAME" = "osx" ] && [ "$GNUPLOT" = "yes" ]; then
  