Uncaught TypeError: Converting circular structure to JSON

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

**Atom Version**: 0.192.0
**System**: Mac OS X 10.10.3
**Thrown From**: [preview](https://github.com/Glavin001/atom-preview) package, v0.13.7
### Stack Trace

Uncaught TypeError: Converting circular structure to JSON

```
At /Users/stevenbuelow/.atom/packages/preview/node_modules/analytics-node/node_modules/superagent/lib/node/index.js:801

TypeError: Converting circular structure to JSON
at stringify (native)
at Request.end (/Users/stevenbuelow/.atom/packages/preview/node_modules/analytics-node/node_modules/superagent/lib/node/index.js:801:29)
at attemptRetry (/Users/stevenbuelow/.atom/packages/preview/node_modules/analytics-node/node_modules/superagent-retry/lib/index.js:38:21)
at Request.end (/Users/stevenbuelow/.atom/packages/preview/node_modules/analytics-node/node_modules/superagent-retry/lib/index.js:48:12)
at Analytics.flush (/Users/stevenbuelow/.atom/packages/preview/node_modules/analytics-node/lib/index.js:159:6)

```
### Commands

```
3x -3:08.5 preview:toggle (atom-text-editor.editor)
-1:51.8 preview:toggle-options (atom-pane.pane)
-1:02.5 preview:toggle (ul.list-inline.tab-bar.inset-panel)
4x -0:47.0 core:backspace (atom-text-editor.editor.is-focused)
-0:31.2 core:save (atom-pane.pane)
3x -0:17.4 core:backspace (atom-text-editor.editor.is-focused)
```
### Config

``` json
{
"core": {
"themes": [
"atom-dark-ui",
"atom-dark-syntax"
],
"disabledPackages": [
"atom-terminal-panel",
"preview-plus"
]
},
"preview": {
"_analyticsUserId": "11bef307-dca2-41fc-b3f7-fd92098a209c"
}
}
```
### Installed Packages

``` coffee
# User
atom-typescript, v2.15.13
autocomplete-plus, v2.11.0
emmet, v2.3.7
linter, v0.12.0
preview, v0.13.7
terminal-status, v1.6.5

# Dev
No dev packages
```

The report points to superagent/lib/node/index.js:801, superagent-retry/lib/index.js, and analytics-node/lib/index.js:159 in the preview package. The reproduction steps are placeholders, so first reproduce the failure using the listed Atom commands and versions, then trace Analytics.flush and Request.end. Done when the preview action no longer produces the uncaught circular-structure error.

Written by the indexing model from the issue text.