update dependencies

[micahstubbs]

node-sass is old, and shows an error on modern 64-bit macs.

on yarn buildWatch:

ERROR in ./public/css/main.scss
Module build failed: Error: Node Sass does not yet support your current environment: OS X 64-bit with Unsupported runtime (59)
For more information on which environments are supported please see:
https://github.com/sass/node-sass/releases/tag/v3.13.1

other packages show warnings on yarn install:

warning [email protected]: 🙌  Thanks for using Babel: we recommend using babel-preset-env now: please read babeljs.io/env to update!
warning blockbuilder-search > [email protected]: 🙌  Thanks for using Babel: we recommend using babel-preset-env now: please read babeljs.io/env to update!
warning blockbuilder-search > superagent > [email protected]: Old versions of Formidable are not compatible with the current Node.js; Upgrade to 1.2.0 or later
warning bragi-browser > browserify > glob > [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
warning [email protected]: react-tools is deprecated. For more information, visit https://fb.me/react-tools-deprecated
warning css-loader > cssnano > autoprefixer > [email protected]: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
warning css-loader > cssnano > postcss-merge-rules > [email protected]: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
warning css-loader > cssnano > postcss-merge-rules > caniuse-api > [email protected]: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.