Not delaying auto increment columns by default any more.

It is still possible to do it by adding 'delayAutoIncrement' to the strategy.
Also adding unit tests for this method, they are needed.
Fixing test case after Ammar's comments.
Merge pull request #155 from youtube/replication

Not delaying auto increment columns by default any more.
Merge branch 'replication'
Merge branch 'master' into resharding

Conflicts:
	go/vt/mysqlctl/split.go
	go/vt/worker/split_clone_test.go