Refactor as submodule for other projects

.travis.yml

-env:
-    global:
-        - REPO_DIR=tornado
-        - BUILD_COMMIT=v4.3.0
-        - BUILD_DEPENDS=
-        - TEST_DEPENDS=
-
-sudo: required
-dist: trusty
-services:
-  - docker
-language:
-  - python
-
-matrix:
-  include:
-    - os: linux
-      python: 2.7
-    - os: linux
-      python: 3.4
-    - os: linux
-      python: 3.5
-    - os: osx
-      language: objective-c
-      env: TRAVIS_PYTHON_VERSION=2.7
-    - os: osx
-      language: objective-c
-      env: TRAVIS_PYTHON_VERSION=3.4
-    - os: osx
-      language: objective-c
-      env: TRAVIS_PYTHON_VERSION=3.5
-
-before_install:
-    - source travis_steps.sh
-    - before_install
-
-install:
-    - git clone https://github.com/facebook/tornado
-    - build_wheels
-    - install_wheel
-
-script:
-    - ls wheelhouse
-    - python -c 'import tornado; print(tornado.__file__)'

manylinux @ 5771b771

-Subproject commit 061dc2f9001caf621a348c134fba4674048e08e8
+Subproject commit 5771b77132f410aef1c0ef0e6c16ad04047a1d44

travis_linux_steps.sh

 #!/bin/bash
 # Travis steps for Linux
-set -ex
+set -e
 
-BUILD_SCRIPT=${BUILD_SCRIPT:-/io/manylinux/build_package.sh}
+ROOT_DIR=$(dirname "${BASH_SOURCE[0]}")
+UTIL_DIR=${UTIL_DIR:-${ROOT_DIR}/manylinux}
+BUILD_SCRIPT=${BUILD_SCRIPT:-/io/$UTIL_DIR/build_package.sh}
 
 function before_install {
     virtualenv --python=python venv
@@ -43,6 +45,7 @@ function build_plat_wheels {
     docker pull $docker_image
     if [ "$plat" == "i686" ]; then local intro_cmd=linux32; fi
     docker run --rm \
+        -e UTIL_DIR=$UTIL_DIR \
         -e PYTHON_VERSION=$TRAVIS_PYTHON_VERSION \
         -e UNICODE_WIDTHS=$UNICODE_WIDTHS \
         -e BUILD_DEPENDS=$BUILD_DEPENDS \

travis_osx_steps.sh

 #!/bin/bash
+# Install and wheel building steps on OSX
 set -e
 
 # Get needed utilities
-ROOT_DIR=$(dirname "$BASH_SOURCE[0]}")
+ROOT_DIR=$(dirname "${BASH_SOURCE[0]}")
 TERRYFY_DIR=$ROOT_DIR/terryfy
 source $TERRYFY_DIR/travis_tools.sh
 

travis_steps.sh

 #!/bin/bash
+# Update submodules
+git submodule update --init --recursive
+
 WHEELHOUSE=$PWD/wheelhouse
+
+MULTIBUILD_DIR=$(dirname "${BASH_SOURCE[0]}")
+
 if [ !-d $WHEELHOUSE ]; then mkdir wheelhouse; fi
 if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
-    source travis_osx_steps.sh
+    source $MULTIBUILD_DIR/travis_osx_steps.sh
     whl_tail="*.whl"
 else
-    source travis_linux_steps.sh
-    whl_tail="*manylinux1_x86_64.whl"
+    source $MULTIBUILD_DIR/travis_linux_steps.sh
+    # Selects narrow build on Python 2.7
+    whl_tail="*m-manylinux1_x86_64.whl"
 fi
 
 function install_wheel {