Bump formastic to ~> 3.0
style update in CSVBuilder
don't use !important in SVG color mixin

Previously you had to do this to use your own color:

```ruby
ActiveAdmin::Iconic.icon(:check, color: '#8daa92 !important')
```

Now you can drop the !important
Merge pull request #3432 from strivedi183/update_formastic

Bump formastic to ~> 3.0
remove formtastic locale keys
use formtastic_i18n gem