Fix #28: WIP - Add initial Jest test for a React component.
Builds off PR #26.
- Adds Jest/Enzyme and the first part of a simple React component test, which can be executed via 'npm run test'.
- Adds eslint rules for Jest
- Adds new devDeps:
- babel-jest: Compiles JS code using Babel in Jest tests; this means Babel is run on any files loaded by Jest (and these files are transformed based on .babelrc).
- babel-preset-env: Compiles ES2015+ down to ES5. Currently this is so we can use 'import' in Node.js for the Jest tests (Jest runs in Node); we add additional rules in .babelrc so that we only perform Babel transforms that are needed for the current Node environment, rather than transforming everything to ES5, which is not needed for Firefox.
- enzyme: JS testing library for React