Bump Capybara version for Chrome headless fixes

Gemfile

@@ -331,7 +331,7 @@ group :development, :test do
   # Generate Fake data
   gem 'ffaker', '~> 2.4'
 
-  gem 'capybara', '~> 2.6.2'
+  gem 'capybara', '~> 2.15'
   gem 'capybara-screenshot', '~> 1.0.0'
   gem 'selenium-webdriver', '~> 2.53'
 

Gemfile.lock

@@ -98,9 +98,9 @@ GEM
       bundler (~> 1.2)
       thor (~> 0.18)
     byebug (9.0.6)
-    capybara (2.6.2)
+    capybara (2.15.1)
       addressable
-      mime-types (>= 1.16)
+      mini_mime (>= 0.1.3)
       nokogiri (>= 1.3.3)
       rack (>= 1.0.0)
       rack-test (>= 0.5.4)
@@ -465,6 +465,7 @@ GEM
     method_source (0.8.2)
     mime-types (2.99.3)
     mimemagic (0.3.0)
+    mini_mime (0.1.4)
     mini_portile2 (2.1.0)
     minitest (5.7.0)
     mmap2 (2.2.7)
@@ -908,7 +909,7 @@ GEM
       expression_parser
       rinku
     xml-simple (1.1.5)
-    xpath (2.0.0)
+    xpath (2.1.0)
       nokogiri (~> 1.3)
 
 PLATFORMS
@@ -940,7 +941,7 @@ DEPENDENCIES
   browser (~> 2.2)
   bullet (~> 5.5.0)
   bundler-audit (~> 0.5.0)
-  capybara (~> 2.6.2)
+  capybara (~> 2.15)
   capybara-screenshot (~> 1.0.0)
   carrierwave (~> 1.1)
   charlock_holmes (~> 0.7.3)