Contributor bug fixes and updated copy

Some bug fixes for contributors (mostly around deleting) and copy updates to the Home and About page.

#73

#72

Contributors and Private Flickr Photos

Summary

feature/oauth #69
feature/contributors #70

Migrations

Required for contributors stuff.

Phoenix 1.4 and dependencies housekeeping

Upgrade to Phoenix 1.4 with a slew of other dependency upgrades.

Treelib🌲

It's about time I start tagging things. 👍

Don't hate me for my liberal use of emojis in commit messages.