* Add support for Rails 6.0 to `ViewContext::BuildStrategy`
In Rails 6.0 the API for `ActionView::Base.new` is changing.
`ActionView::Base.new` now take arguments [1], otherwise you
will see the following deprecation warning:
```
DEPRECATION WARNING: ActionView::Base instances should be constructed with a lookup context, assignments, and a controller.
```
[1] e17fe52e0e
`ViewContext::BuildStrategy::Fast` does not have lookup context, so use `empty`
method instead of `new` to build instance.
* Bump a Rails version of dummy application
Also bump a sqlite version because Rails 6.0 requires upper sqlite
1.4.0.
* Add `ApplicationController` to dummy application
Because Action Text expects `ApplicationController` exists.
Ref: https://github.com/rails/rails/issues/35749#issuecomment-525083643
* Test against Rails 6.0 that only supported Ruby versions
89ec4b70f4