Failed to activate the atom-medium package

[Enter steps to reproduce:]

1. ...
2. ...

**Atom**: 1.39.1 x64
**Electron**: 3.1.10
**OS**: Mac OS X 10.14.6
**Thrown From**: [atom-medium](https://github.com/ericadamski/atom-medium-upload) package 2.0.1

### Stack Trace

Failed to activate the atom-medium package

```
At this._acquireAccessToken is not a function

TypeError: this._acquireAccessToken is not a function
at MediumClient.exchangeRefreshToken (/packages/atom-medium/node_modules/medium-sdk/lib/mediumClient.js:154:8)
at tryCatcher (/packages/atom-medium/node_modules/rxjs/util/tryCatch.js:6:31)
at BoundCallbackObservable._subscribe (/packages/atom-medium/node_modules/rxjs/observable/BoundCallbackObservable.js:204:64)
at BoundCallbackObservable.Observable._trySubscribe (/packages/atom-medium/node_modules/rxjs/Observable.js:172:25)
at BoundCallbackObservable.Observable.subscribe (/packages/atom-medium/node_modules/rxjs/Observable.js:160:93)
at storeToken (/packages/atom-medium/lib/authenticate.js:107:12)
at hasToken (/packages/atom-medium/lib/authenticate.js:63:9)
at authenticate (/packages/atom-medium/lib/authenticate.js:116:12)
at user (/packages/atom-medium/lib/client.js:15:12)
at User.componentDidMount (/packages/atom-medium/lib/components/user.jsx:57:9)
at Vh (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:216:198)
at Zh (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:220:182)
at /packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:250:268
at Object.exports.unstable_runWithPriority (/packages/hydrogen-python/node_modules/scheduler/cjs/scheduler.production.min.js:18:163)
at Fi (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:250:203)
at Di (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:249:383)
at Yh (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:248:144)
at Xh (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:245:332)
at qf (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:243:86)
at Ji (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:253:14)
at Ki (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:253:92)
at Pi.render (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:261:109)
at /packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:264:395
at Hi (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:251:73)
at Si (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:264:328)
at render (/packages/hydrogen-python/node_modules/react-dom/cjs/react-dom.production.min.js:266:373)
at /packages/atom-medium/lib/medium-upload-view.js:15:9)
at Object.activate (/packages/atom-medium/lib/medium-upload.js:18:33)
at Package.activateNow (/Applications/Atom.app/Contents/Resources/app/static/:11:3421604)
at activationCommandSubscriptions.add.commandRegistry.onWillDispatch.o (/Applications/Atom.app/Contents/Resources/app/static/:14:1879)
```

### Commands

```
-0:03.7.0 medium-upload:toggle (input.hidden-input)
```

### Non-Core Packages

```
atom-clock 0.1.17
atom-material-ui 2.1.3
atom-medium 2.0.1
cacher 1.0.3
export-html 3.1.0
gruvbox-plus-syntax 1.3.1
Hydrogen 2.10.3
hydrogen-python 0.0.8
language-latex 1.2.0
latex 0.50.2
markdown-themeable-pdf 1.2.1
markdown-writer 2.11.6
platformio-ide-terminal 2.9.1
python-autopep8 0.1.3
python-indent 1.2.3
wordcount 3.1.0
```