update dependencies

@micahstubbs is already working on this.

Since Aug 17, 2018.

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 babel-preset-es2015@6.24.1: 🙌 Thanks for using Babel: we recommend using babel-preset-env now: please read babeljs.io/env to update!
warning blockbuilder-search > babel-preset-es2015@6.24.1: 🙌 Thanks for using Babel: we recommend using babel-preset-env now: please read babeljs.io/env to update!
warning blockbuilder-search > superagent > formidable@1.0.17: Old versions of Formidable are not compatible with the current Node.js; Upgrade to 1.2.0 or later
warning bragi-browser > browserify > glob > minimatch@2.0.10: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
warning react-tools@0.13.3: react-tools is deprecated. For more information, visit https://fb.me/react-tools-deprecated
warning css-loader > cssnano > autoprefixer > browserslist@1.7.7: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
warning css-loader > cssnano > postcss-merge-rules > browserslist@1.7.7: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
warning css-loader > cssnano > postcss-merge-rules > caniuse-api > browserslist@1.7.7: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
```