Uncaught TypeError: undefined is not a function

[Enter steps to reproduce below:]
1. ...
2. ...

**Atom Version**: 0.184.0
**System**: Mac OS X 10.10.2
**Thrown From**: [preview](https://github.com/Glavin001/atom-preview) package, v0.13.4
### Stack Trace

Uncaught TypeError: undefined is not a function

```
At /Users/James/.atom/packages/preview/lib/preview-view.coffee:74

TypeError: undefined is not a function
at new PreviewView (/Users/James/.atom/packages/preview/lib/preview-view.coffee:74:40)
at /Users/James/.atom/packages/preview/lib/preview.coffee:41:26
at wrappedOpener (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/workspace.js:578:16)
at Workspace.module.exports.Workspace.openURIInPane (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/workspace.js:495:22)
at Workspace.module.exports.Workspace.open (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/workspace.js:428:19)
at Object.module.exports.toggle (/Users/James/.atom/packages/preview/lib/preview.coffee:81:20)
at atom-workspace. (/Users/James/.atom/packages/preview/lib/preview.coffee:23:8)
at atom-workspace.handler (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/space-pen-extensions.js:115:32)
at atom-workspace.jQuery.event.dispatch (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/node_modules/space-pen/vendor/jquery.js:4681:9)
at atom-workspace.elemData.handle (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/node_modules/space-pen/vendor/jquery.js:4359:46)
at CommandRegistry.module.exports.CommandRegistry.handleCommandEvent (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/command-registry.js:243:29)
at CommandRegistry.handleCommandEvent (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/command-registry.js:3:61)
at CommandRegistry.module.exports.CommandRegistry.dispatch (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/command-registry.js:156:19)
at EventEmitter. (/opt/homebrew-cask/Caskroom/atom/latest/Atom.app/Contents/Resources/app/src/window-event-handler.js:75:30)
at EventEmitter.emit (events.js:116:17)

```
### Commands

```
```
### Config

``` json
{
"core": {
"disabledPackages": [
"merge-conflicts",
"git-merge-conflicts",
"Remote-FTP",
"remote-sync",
"SFTP-deployment",
"CoffeeCompile"
],
"themes": [
"atom-dark-ui",
"monokai-dark"
]
},
"preview": {
"_analyticsUserId": "a5f82a18-132e-4821-8e22-766abcf1e00b"
}
}
```
### Installed Packages

``` coffee
# User
preview, v0.13.4

# Dev
No dev packages
```

Start with lib/preview-view.coffee at line 74 and follow its construction from lib/preview.coffee at lines 41 and 81. Reproduce by opening the preview in Atom 0.184.0 on Mac OS X 10.10.2, then trace the reported TypeError. Done means the preview opens without the uncaught exception.

Written by the indexing model from the issue text.