bump capybara

Gemfile

@@ -198,7 +198,7 @@ group :test do
   gem 'rails-controller-testing', '~> 1.0.2'
 
   gem 'aws-sdk', '~> 2.10.1'
-  gem 'capybara', '~> 2.14.0'
+  gem 'capybara', '~> 2.15.0'
   gem 'capybara-screenshot', '~> 1.0.14'
   gem 'fuubar', '~> 2.2.0'
   gem 'capybara-select2', git: 'https://github.com/goodwill/capybara-select2', ref: '585192e'

Gemfile.lock

@@ -179,9 +179,9 @@ GEM
       thor (~> 0.19)
     builder (3.2.3)
     byebug (9.0.6)
-    capybara (2.14.4)
+    capybara (2.15.4)
       addressable
-      mime-types (>= 1.16)
+      mini_mime (>= 0.1.3)
       nokogiri (>= 1.3.3)
       rack (>= 1.0.0)
       rack-test (>= 0.5.4)
@@ -358,6 +358,7 @@ GEM
       actionpack (>= 3.2.0, < 5.3)
     method_source (0.8.2)
     mime-types (2.99.3)
+    mini_mime (0.1.4)
     mini_portile2 (2.3.0)
     minisyntax (0.2.5)
     minitest (5.10.3)
@@ -634,7 +635,7 @@ DEPENDENCIES
   bcrypt (~> 3.1.6)
   bootsnap (~> 1.1.2)
   bourbon (~> 4.3.4)
-  capybara (~> 2.14.0)
+  capybara (~> 2.15.0)
   capybara-ng (~> 0.2.7)
   capybara-screenshot (~> 1.0.14)
   capybara-select2!