This PR adds ability to accept arrays which allows you to require multiple values in one method. so instead of this:
```ruby
params.require(:person).require(:first_name)
params.require(:person).require(:last_name)
```
Here it will be one line for each params, so say if I require 10params, it will be 10lines of repeated code which is not dry. So I have added new method which does this in one line:
```ruby
params.require(:person).require([:first_name, :last_name])
```
Comments welcome
Non-kwargs requests are deprecated now.
Guides are updated as well.
`post url, nil, nil, { a: 'b' }` doesn't make sense.
`post url, params: { y: x }, session: { a: 'b' }` would be an explicit way to do the same
When the value for the required key is empty an ActionController::ParameterMissing is raised which gets caught by ActionController::Base and turned into a 400 Bad Request reply with a message in the body saying the key is missing, which is misleading.
With these changes, ActionController::EmptyParameter will be raised which ActionController::Base will catch and turn into a 400 Bad Request reply with a message in the body saying the key value is empty.
