Handle circular refs in schema

I use a circular model for my JSON schema. So as an example JSON, something like this:

```json
{
"guides": [{
// This can go on forever recursively
"children": [{
"children": [{
"name": "My Item"
}]
}]
}]
}
```

Here is JSON schema
```json
{
"$schema": "http://json-schema.org/draft-07/schema#",
"definitions": {
"DocsConfigNavigation": {
"anyOf": [
{
"$ref": "#/definitions/DocsConfigNavigationPage"
},
{
"$ref": "#/definitions/DocsConfigNavigationCategory"
}
]
},
"DocsConfigNavigationCategory": {
"properties": {
"children": {
"items": {
"$ref": "#/definitions/DocsConfigNavigation"
},
"type": "array"
}
},
"required": [
"children"
],
"type": "object"
},
"DocsConfigNavigationPage": {
"properties": {
"name": {
"type": "string"
}
},
"type": "object"
}
},
"properties": {
"guides": {
"items": {
"$ref": "#/definitions/DocsConfigNavigation"
},
"type": "array"
}
},
"type": "object"
}

```

This results in the following error:

```
$ wetzel docs.schema.json
/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/defaultValue.js:14
function defaultValue(value, fallback) {
^

RangeError: Maximum call stack size exceeded
at defaultValue (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/defaultValue.js:14:22)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:28:24)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:96:32)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:96:32)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:90:16)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:96:32)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:96:32)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:96:32)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:90:16)
at replaceRef (/Users/brunnel6/.npm-packages/lib/node_modules/wetzel/lib/replaceRef.js:96:32)
```

Reproduce the failure with the circular schema from the issue, then inspect lib/replaceRef.js and lib/defaultValue.js, where the stack trace points. Check how the wetzel command processes the schema and determine the expected handling and output for circular references, since the issue does not specify it. Done should include a verified run that no longer overflows the call stack.

Written by the indexing model from the issue text.