Add travis CI config

scripts/travis-build.sh

+#!/bin/sh
+
+set -ex
+
+setup_env() {
+  # Travis sets CC/CXX to the system toolchain, so our .travis.yml
+  # exports USE_{CC,CXX} for this script to use.
+  if [ -n "$USE_CC" ]; then
+      export CC=$USE_CC
+  fi
+  if [ -n "$USE_CXX" ]; then
+      export CXX=$USE_CXX
+  fi
+  # Use -jN for faster builds. Travis build machines under Docker
+  # have a lot of cores, but are memory-limited, so the kernel
+  # will OOM if we try to use them all, so use at most 4.
+  # See https://github.com/travis-ci/travis-ci/issues/1972
+  export NCPUS=$(getconf _NPROCESSORS_ONLN)
+  export JOBS=$(( $NCPUS < 4 ? $NCPUS : 4 ))
+}
+
+build() {
+  ./configure
+  make -j${JOBS} check
+}
+
+main() {
+  setup_env
+  build
+}
+
+main "$@"