feature: Change to a Rails 4 ActiveModel validator.

[schwern]

Rails 4 introduced ActiveModel, ActiveModel::Validations and ActiveModel::EachValidator. Instead of injecting ourselves into ActiveRecord::Base, we will be automatically picked up. This fixes #10.

We can now also be used on ActiveModel as well as ActiveRecord. This simplifies testing.

Also

• rspec-rails was dropped becasue it seems to want all of Rails loaded.
  We only needed one convenience method, errors_on. It has been copied into our test model.
• Bumped our runtime dependency to activemodel >= 4.0. Dropped the others.
• Dropped the development dependency on all of Rails. We only need ActiveModel.

[KimNorgaard]

I am in a bit of a pickle here since I havn't touched rails since v3. How does one go about supporting backwards compatibility for a gem such as this?

[schwern]

@KimNorgaard Since most of the code remains the same, we could write a module with all the common code, and then maintain Rails v3 and Rails v4+ wrapper files and load one or the other as appropriate for the Rails version.

However, considering that the last release of Rails v3 was 10 years ago, I would say it's much simpler to bump to version 2 to indicate a breaking change. Existing Rails v3 users would be safe as they have gem 'validates_hostname', '~> 1', and document they should remain with v1, and everyone else move to gem 'validates_hostname', '~> 2'

[KimNorgaard]

@KimNorgaard Since most of the code remains the same, we could write a module with all the common code, and then maintain Rails v3 and Rails v4+ wrapper files and load one or the other as appropriate for the Rails version.

However, considering that the last release of Rails v3 was 10 years ago, I would say it's much simpler to bump to version 2 to indicate a breaking change. Existing Rails v3 users would be safe as they have gem 'validates_hostname', '~> 1', and document they should remain with v1, and everyone else move to gem 'validates_hostname', '~> 2'

I'm fine going forwards with v2.0.0. Please resolve the conflicts, update version info and let me know and I'll restart the review, tag the release and release a new gem.