Fix fatal error when using `annotate` with ActiveRecord 4.1

The fatal error was introduced with commit fc31d85. The method
`supports_foreign_keys?` is only available on ActiveRecord versions
>= 4.2.

Fixes issue 316.

Fix rubocop problems due to version change

 - Replace SpaceAroundKeyword with SpaceAfterControlKeyword
 - Use an explicit rubocop version to avoid breakages during PRs

Don't leave wrapper when removing annotations

Added coveralls.

Reduce rubocop offenses and don't include activeadmin models by default

Reduced the Cyclomatic complexity.
#330 By default didn't annotate activeadmin models.
This close #330

Fix the link to rubygems

Add ruby head to travis and integrate with rubocop 

Added coveralls and code climate gems.

# Conflicts:
#	Gemfile

Support hide_limit_column_types options in annotate_models.rake

Added Simplecov.

Added Active admin models.

Do not annotate controllers, helpers and scaffolds by default (revert to behavior from previous version)

Add :ignore_routes option to skip routes which should not be annotated based on regex

fix code markup in docs

Run tests by Ruby 2.3.0