Replace _.includes (removed from underscore.string) with _.include

I don't know when, but this method was removed from `underscore.string`.
```
$ node_modules/.bin/sequelize init
```
```
Sequelize [CLI: v0.2.0, ORM: v2.0.0-dev12]

/Users/<...>/node_modules/sequelize-cli/lib/helpers/migration-helper.js:18
      if (_.includes(line, '//')) {
            ^
TypeError: Object function lodash(value) {
...
    } has no method 'includes'
    at /Users/<...>/node_modules/sequelize-cli/lib/helpers/migration-helper.js:18:13

```

Please, update npm ASAP.
It's deployment time.

Thanks=)