title: Mongoid 7 + mongoid-rspec compatibility issues
body: <p>I am integrating mongoid-rspec with Mongoid 7 and while running the command rspec it show me below mentioned error trace:</p>
  
  <pre><code>cannot load such file -- mongoid/relations
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `block in require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:258:in `load_dependency'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/mongoid-rspec-4.0.0/lib/matchers/associations.rb:1:in `&lt;top (required)&gt;'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `block in require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:258:in `load_dependency'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/mongoid-rspec-4.0.0/lib/mongoid/rspec.rb:13:in `&lt;top (required)&gt;'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `block in require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:258:in `load_dependency'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/activesupport-5.1.6/lib/active_support/dependencies.rb:292:in `require'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@wavedio/gems/mongoid-rspec-4.0.0/lib/mongoid-rspec.rb:1:in `&lt;top (required)&gt;'
  # /home/xxxxxxxx/.rvm/gems/ruby-2.4.1@global/gems/bundler-1.16.1/lib/bundler.rb:114:in `require'
  
  Configured mongoid-rspec using this link https://github.com/mongoid/mongoid-rspec
  </code></pre>
  
  <p>Rails - 5.1.6 </p>
  
  <p>Ruby - 2.4.1</p>