Exception thrown after updating custom field via API

[patrickfish]

Issue type: Bug report

Python version: 2.7.9
NetBox version: 2.0.3

1. Create custom field (I used a boolean) tied to dcim > site
2. Do a PUT/POST against a site writing to that custom field, example:

{
  "name": "206",
  "slug": "206",
  "custom_fields":{"anira_ready":true}
}

3. Attempt to load the site via web browser: $netbox/dcim/sites/206/

Error is:

<type 'exceptions.ValueError'>

invalid literal for int() with base 10: 'True'

[jeremystretch]

This is happening because custom field values are not being properly serialized when entered via the API.