Support conversion of implicit spec types in rspec-rails

[yujinakayama]

• Consider making example group mixins more explicit rspec/rspec-rails#662
• Make filetype infer opt-in rspec/rspec-rails#970 (comment)
• Add deprecation to 2.99 to instruct users to use infer_spec_type_from_file_location! when upgrading rspec/rspec-rails#1004

[yujinakayama]

@myronmarston Currently I'm implementing this conversion, but I'm not sure whether this conversion should be enabled by default since the implicit mixins still can be considered as the default behavior in rspec-rails 3.0:

• config.infer_spec_type_from_file_location! is enabled in the auto-generated spec_helper.rb.
• The documentation and the template are still omitting the :type metadata.

What do you think?

[myronmarston]

Setting the type explicitly (even if the config.infer_spec_type_from_file_location! option is used) causes no problems and will make it easier for the user to stop using that config option in the future if they want, so I think it's probably worth while to do it anyway.

@cupakromer, what do you think? Also, as @yujinakayama pointed out, there's some docs and templates we should probably update :).

[yujinakayama]

@myronmarston Thanks. It makes sense. I'll make the conversion enabled by default.

[cupakromer]

I agree with turning it on by default. Agreed, a few more updates need to be made in rspec-rails for this.