auto-incrementing primary keys in Sqlite
http://www.sqlite.org/autoinc.html  - i will see about a fix
 Because SQLite incurs additional overhead to guarantee monotonically incrementing PKs, I will keep the default behavior which simply guarantees they are unique.

If you would like to use an autoincrementing primary key, try this in your code:

``` python

db = SqliteDatabase('mydb.db', fields={'primary_key': 'INTEGER AUTOINCREMENT'})
```

Or

``` python

db.register_fields({'primary_key': 'INTEGER AUTOINCREMENT'})
```
 I thought about that, too; unfortunately Sqlite complains about a syntax error. The "invalid" SQL looks like this:

CREATE TABLE "test" ("id" INTEGER AUTOINCREMENT NOT NULL PRIMARY KEY, ...)
I believe, the AUTOINCREMENT should be positioned after PRIMARY KEY.
 I'm thinking about trying to refactor all the DDL stuff.  Hopefully that might make something like this change easier...currently the ordering of the clauses is somewhat hardcoded :goberserk: 
 Still not work.

1 `db = SqliteDatabase('mydb.db', fields={'primary_key': 'INTEGER AUTOINCREMENT'})` got below error:

`peewee.OperationalError: near "AUTOINCREMENT": syntax error`

SQL is:
`u'CREATE TABLE "customer" ("id" INTEGER AUTOINCREMENT NOT NULL PRIMARY KEY, "name" VARCHAR(255) NOT NULL, "upper_name" VARCHAR(255) NOT NULL, "remark" VARCHAR(255) NOT NULL)'`

2 `db.register_fields({'primary_key': 'INTEGER AUTOINCREMENT'})` has no effect at all
 This is for a much older version of Peewee. Check out http://docs.peewee-orm.com/en/latest/peewee/playhouse.html#PrimaryKeyAutoIncrementField
 So, I have to define id manually? And, `PrimaryKeyAutoIncrementField` is only for Sqlite, right?

```
Class User(Model):
    id = PrimaryKeyAutoIncrementField()
    name = CharField()
```
 Peewee includes an autoincrement pk by default for all databases. For sqlite, there are different types, rowid and a special autoincrement type. See:

http://www.sqlite.org/autoinc.html

I have a question regarding auto-incrementing primary keys. As far as I can see from tests, in MySQL, primary key columns are created with AUTO_INCREMENT by default, whereas in Sqlite databases the primary key of an insert may not be unique forever if some rows are deleted. As far as I understand, the equivalent of AUTO_INCREMENT (MySQL) is AUTOINCREMENT in Sqlite.
I haven't yet been able to figure out how to use this feature with Sqlite without modifying peewee itself (model._meta.auto_increment doesn't seem to have an effect).

Thank you
