ARROW-3301: [Website] Update Jekyll and Bootstrap 4

Screenshot:

![127 0 0 1_4000_ ipad pro](https://user-images.githubusercontent.com/70274/45920083-b2953300-be9f-11e8-84b8-381570ae8245.png)

Author: Korn, Uwe <Uwe.Korn@blue-yonder.com>
Author: Wes McKinney <wesm+git@apache.org>

Closes #2607 from xhochy/ARROW-3301 and squashes the following commits:

0e8949aa1 <Wes McKinney> Simple text about advantages of columnar memory layout
2fb70d63a <Korn, Uwe> Remove placeholder text
b92793982 <Korn, Uwe> Add license header to main.js
c83e3db6a <Korn, Uwe> ARROW-3301:  Update Jekyll and Bootstrap 4
14 files changed
tree: d8d45ab3f05d6b5538b419eab19ac5244f7808fe
  1. _data/
  2. _docs/
  3. _includes/
  4. _layouts/
  5. _posts/
  6. _release/
  7. _sass/
  8. assets/
  9. css/
  10. img/
  11. scripts/
  12. .gitignore
  13. _config.yml
  14. blog.html
  15. committers.html
  16. Gemfile
  17. index.html
  18. install.md
  19. powered_by.md
  20. README.md
README.md

Apache Arrow Website

Development instructions

If you are planning to publish the website, you must first clone the arrow-site git repository:

git clone --branch=asf-site https://git-wip-us.apache.org/repos/asf/arrow-site.git asf-site

Now, with Ruby >= 2.1 installed, run:

gem install jekyll bundler
bundle install

# This imports the format Markdown documents so they will be rendered
scripts/sync_format_docs.sh

bundle exec jekyll serve

Publishing

After following the above instructions the base site/ directory, run:

JEKYLL_ENV=production bundle exec jekyll build
rsync -r build/ asf-site/
cd asf-site
git status

Now git add any new files, then commit everything, and push:

git push

Updating Code Documentation

To update the documentation, run the script ./dev/gen_apidocs.sh. This script will run the code documentation tools in a fixed environment.

C (GLib)

First, build Apache Arrow C++ and Apache Arrow GLib.

mkdir -p ../cpp/build
cd ../cpp/build
cmake .. -DCMAKE_BUILD_TYPE=debug
make
cd ../../c_glib
./autogen.sh
./configure \
  --with-arrow-cpp-build-dir=$PWD/../cpp/build \
  --with-arrow-cpp-build-type=debug \
  --enable-gtk-doc
LD_LIBRARY_PATH=$PWD/../cpp/build/debug make GTK_DOC_V_XREF=": "
rsync -r doc/reference/html/ ../site/asf-site/docs/c_glib/

Javascript

cd ../js
npm run doc
rsync -r doc/ ../site/asf-site/docs/js

Then add/commit/push from the site/asf-site git checkout.