TypeError w/ new app

## Expected Behavior
Can add a component

## Current Behavior
Calcite-react throws a type error when [creating a new app](https://reactjs.org/docs/create-a-new-react-app.html#create-react-app) with create-react-app and replacing index.js / App.js with the calcite-react [getting started snippets](https://calcite-react.netlify.com/)

## Context + Screenshots
Error message
```
Uncaught TypeError: (0 , _helpers.fontSize) is not a function
at Object../node_modules/calcite-react/CalciteThemeProvider/CalciteThemeProvider.js (CalciteThemeProvider.js:97)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Object../node_modules/calcite-react/CalciteThemeProvider/index.js (index.js:25)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Object../node_modules/calcite-react/utils/helpers.js (helpers.js:10)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Object../node_modules/calcite-react/Button/Button-styled.js (Button-styled.js:10)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Object../node_modules/calcite-react/Button/Button.js (Button.js:12)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Object../node_modules/calcite-react/Button/index.js (index.js:19)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Module../src/App.js (index.css:3)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Module../src/index.js (index.css?e32c:37)
at __webpack_require__ (bootstrap:785)
at fn (bootstrap:150)
at Object.1 (serviceWorker.js:137)
at __webpack_require__ (bootstrap:785)
at checkDeferredModules (bootstrap:45)
at Array.webpackJsonpCallback [as push] (bootstrap:32)
at main.chunk.js:1
```

## Your Environment

* Version used: 0.47.0
* Browser Name and version: chrome / firefox latest
* Operating System and version (desktop or mobile): NA
* Link to your project: NA

package.json dependencies
```
"@testing-library/jest-dom": "^4.2.4",
"@testing-library/react": "^9.3.2",
"@testing-library/user-event": "^7.1.2",
"calcite-react": "^0.47.0",
"react": "^16.12.0",
"react-dom": "^16.12.0",
"react-scripts": "3.3.0"
```