Continuously deploy to GH Pages

[dcecile]

Web links:

• CI comparison
• Deploying from CodeShip to GH Pages
• Semaphore
• AppVeyor

Tasks

• [x] Document deploy steps
• [x] Create fmtCheck
• [x] Set up GitHub Pages project
• [x] Create GitHub Pages README
• [x] Create non-dev HTML files
• [x] Set up links between HTML files
• [x] Set up Shippable CI build
• [x] Disable Shippable CI for non-master branches (long-running branches can open PRs to get CI)
• [x] Enable Shippable CI caching (for SBT and dependencies)
• [x] Set up Shippable deploy to GitHub pages using state (utils) and runSh
• [x] Don't deploy -dev HTML files
• [x] Switch Shippable deploy to use job state (not global state)
• [x] Fix PNG errors
• [x] Make sure Shippable deploy doesn't trigger for PRs
• [x] Fill in all GitHub project and organization links
• [x] Add Shippable badge to README

[dcecile]

Problem with PNG file worked around with Base64 encoding -- to be reverted in #14.

[dcecile]

Note: failure notifications not set up yet