Fix gotrue migrate

[grinkus]

- Do you want to request a feature or report a bug?
Bug

- What is the current behavior?
When running gotrue migrate on a fresh docker instance (with mysql:5.7) it exits with:

DEBU[2018-08-31T21:37:00.283202945Z] Set log level to: debug                      
INFO[2018-08-31T21:37:00.283456644Z] Reading migrations from /usr/local/etc/gotrue/migrations 
INFO[2018-08-31T21:37:00.28450867Z] before status                                
[POP] 2018/08/31 21:37:00 CREATE TABLE schema_migration (
version VARCHAR (255) NOT NULL
) ENGINE=InnoDB;
CREATE UNIQUE INDEX version_idx ON schema_migration (version);
FATA[2018-08-31T21:37:00.289102913Z] Error 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CREATE UNIQUE INDEX version_idx ON schema_migration (version)' at line 4
github.com/netlify/gotrue/vendor/github.com/gobuffalo/pop.(*Connection).timeFunc
	/go/src/github.com/netlify/gotrue/vendor/github.com/gobuffalo/pop/connection.go:184
github.com/netlify/gotrue/vendor/github.com/gobuffalo/pop.(*Query).Exec
	/go/src/github.com/netlify/gotrue/vendor/github.com/gobuffalo/pop/executors.go:19

- If the current behavior is a bug, please provide the steps to reproduce.
On a fresh docker instance run gotrue migrate.

- What is the expected behavior?
DB is successfully inited.

- Please mention your Go version, and operating system version.
Linux 25ffb6af1032 4.15.0-33-generic #36~16.04.1-Ubuntu SMP Wed Aug 15 17:21:05 UTC 2018 x86_64 Linux
golang:1.9.2
As specified in the Dockerfile

[k1ng440]

I am running into the same problem.

[k1ng440]

#188

[k1ng440]

This issue has been solved. Please close it.