Document that `type:'string'` attributes are automigrated as VARCHAR by default and not TEXT (and thus silent truncation if you use long strings and don't specify a columnType)

**Sails version**: 1.0.1
**Node version**: 8.11.1
**NPM version**: 4.0.5
**DB adapter name**: sails-mysql
**DB adapter version**: 1.0.0
**Operating system**: windows/ubuntu

---

I just realized that fields with type 'string' get persisted to database(MySql) silently without any error or warning if their length is over 255 chars.

Its a SERIOUS BUG IMO and must be either resolved quickly or should be explicitly mentioned in documentation of sailsjs or sails-mysql adapter.

I temporarily found a fix about it which is by using the `columnType` attribute.
Eg:
```
description: {
type: 'string',
required: true,
columnType: 'text'
}
```

No file or test is named; start by locating the Sails or sails-mysql documentation covering string attributes and MySQL column types. Verify the stated default and the `columnType: 'text'` example, then document the behavior and truncation risk; done means a newcomer can find and understand this guidance.

Written by the indexing model from the issue text.