Shopify/lhm — pull request #4 by Thibaut (2014-12-22 16:01:20+00:00)
Title: Raise an error when index name is invalid

Prevents this kind of thing:

```ruby
change_table :foo do |m|
m.add_index [:bar], name: 'bar'
end
```

```sql
create index `{:name=>"bar"}` on `lhmn_foo` (`bar`)
```

@arthurnn @camilo
cc @sroysen @SingerWang