Bump rake from 12.3.0 to 12.3.1 (#73)

Bumps [rake](https://github.com/ruby/rake) from 12.3.0 to 12.3.1.
- [Release notes](https://github.com/ruby/rake/releases)
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](ruby/rake@v12.3.0...v12.3.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile.lock

@@ -97,7 +97,7 @@ GEM
       binding_of_caller (>= 0.7)
       pry (>= 0.9.11)
     rainbow (3.0.0)
-    rake (12.3.0)
+    rake (12.3.1)
     rspec (3.7.0)
       rspec-core (~> 3.7.0)
       rspec-expectations (~> 3.7.0)