* Fixes#497 by adding support for an optional new env variable, S3_BUCKET_URL_BASE
* Add a section to README about optional S3 bucket URL base configuration.
* start to create asset list
* begin refactoring overlay component to remove duplicate code
* refactoring of overlays, asset list styles
* changes to add size to asset list
* fixes to asset list
* handle case in which a user hasn't uploaded any assets
* fix bug in which asset list only grabbed first asset
* remove console.log
* update overlay exit styling to use icon mixin
* update eslint and dependencies, fix linting errors that can be fixed with --fix
* fix lots of linting errors
* update eslintrc, fix some linting errors
* fix all server side linting errors, untested
* fix errors that fixing linting errors had caused
* fix client side eslint errors
* fix client side linting errors
* fix refs lint errors
* fix more linting errors
* update eslint and dependencies, fix linting errors that can be fixed with --fix
* fix lots of linting errors
* update eslintrc, fix some linting errors
* fix all server side linting errors, untested
* fix errors that fixing linting errors had caused
* fix client side eslint errors
* fix client side linting errors
* fix refs lint errors
* fix more linting errors
* fix some accessibility linting errors
* fix a lot of linting errors
* fix a billion more linting errors
* hopefully fix all linting errors, still need to test
* fix bugs that fixing linting had caused