Support Rails 5 releases

Thanks to PR #5 by @pedantic-git, supports all of 5.x Rails versions.

Lower Rails dependency to 4.2 to match administrate

This release just changes the Rails dependency:

gem.add_dependency 'rails', '>= 4.2', '< 5.1'

And updates Ruby to 2.4.1 on Travis.

More options for Paperclip field, better development environment.

• Introduces the options thumbnail_style and big_style to control the image sizes that are displayed, by @klaseskilson.
• Better specs, better documentation, Simplecov, Rubocop and CI integration also by @klaseskilson.
• Adds a url_only option for attachments that are not images by @pedantic-git.

Check the updated README for instructions on how to use the new options.

0.0.2

Renames PaperclipField to Paperfield.
Adds spec.