Prepare for 0.9.0

[boie0025]

• Bump ActiveAdmin version
• Bump Rails version
• Bump Devise version
  From @deivid-rodriguez
• Remove unused gemfile and lockfile
• Remove unused stuff from Gemfile
• Use https source to prevent bundler warning

The git source
`git://github.com/activerecord-hackery/ransack-mongoid.git` uses the
`git` protocol, which transmits data without encryption. Disable this
warning with `bundle config git.allow_insecure true`, or switch to the
`https` protocol to keep your data secure.

• Move pry-rails to main group
• bundle update
• Fix RSpec deprecation warning

Requiring `rspec/autorun` when running RSpec via the `rspec` command is
deprecated. Called from
/path/to/activesupport-5.2.2/lib/active_support/dependencies.rb:291:in
`require'.

[boie0025]

Thoughts on waiting for a PR for #138 ?

[grzegorz-jakubiak]

I'd include rubygems badge as well 😉

[boie0025]

@grzegorz-jakubiak Will you please add that and push to this branch?

[grzegorz-jakubiak]

@boie0025 done