Update rubocop requirement to ~> 0.52.1 (#39)

Updates the requirements on [rubocop](https://github.com/bbatsov/rubocop) to permit the latest version.
- [Release notes](https://github.com/bbatsov/rubocop/releases)
- [Changelog](https://github.com/bbatsov/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v0.51.0...v0.52.1)

Gemfile.lock

@@ -74,8 +74,7 @@ GEM
     pry-stack_explorer (0.4.9.2)
       binding_of_caller (>= 0.7)
       pry (>= 0.9.11)
-    rainbow (2.2.2)
-      rake
+    rainbow (3.0.0)
     rake (12.3.0)
     rspec (3.7.0)
       rspec-core (~> 3.7.0)
@@ -90,11 +89,11 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.7.0)
     rspec-support (3.7.0)
-    rubocop (0.51.0)
+    rubocop (0.52.1)
       parallel (~> 1.10)
-      parser (>= 2.3.3.1, < 3.0)
+      parser (>= 2.4.0.2, < 3.0)
       powerpack (~> 0.1)
-      rainbow (>= 2.2.2, < 3.0)
+      rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
     ruby-progressbar (1.9.0)
@@ -129,7 +128,7 @@ DEPENDENCIES
   pry-stack_explorer (~> 0.4.9.2)
   rake (~> 12.0)
   rspec (~> 3.7)
-  rubocop (~> 0.51.0)
+  rubocop (~> 0.52.1)
   simplecov (~> 0.15.1)
 
 BUNDLED WITH

bringit.gemspec

@@ -36,6 +36,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'pry-stack_explorer', '~> 0.4.9.2'
   s.add_development_dependency 'rake', '~> 12.0'
   s.add_development_dependency 'rspec', '~> 3.7'
-  s.add_development_dependency 'rubocop', '~> 0.51.0'
+  s.add_development_dependency 'rubocop', '~> 0.52.1'
   s.add_development_dependency 'simplecov', '~> 0.15.1'
 end