Prepare "coming soon" update for front page

This is a small placeholder that will appear on the public Hub at
https://18f.gsa.gov/hub/ before launch.
Merge pull request #15 from 18F/coming-soon

Prepare "coming soon" update for front page
Tweaks per @afeld's comments in #14
Minor tweak to join_snippet_data per @afeld in #16
Merge pull request #14 from 18F/team-data-private-3

Switch over to consolidated data-private format
Merge pull request #16 from 18F/public-snippets-v3-only

Only publish v3 snippets in public mode
Add join_project_data test; filter "status: Hold"

The "status: Hold" filter is per Leah Bannon's comments in 18F/data-public#5.
Merge branch 'hold-projects' of github.com:18F/hub into hold-projects

Conflicts:
	_plugins/joiner.rb
	_test/joiner_test.rb