Bump rack-dev-mark from 0.7.5 to 0.7.8

Bumps [rack-dev-mark](https://github.com/dtaniwaki/rack-dev-mark) from 0.7.5 to 0.7.8.
- [Release notes](https://github.com/dtaniwaki/rack-dev-mark/releases)
- [Commits](dtaniwaki/rack-dev-mark@v0.7.5...v0.7.8)

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

Author: dependabot-preview[bot]

Gemfile

@@ -27,7 +27,7 @@ gem 'jquery-rails', '~> 4.3.1'
 gem 'rails_autolink', '~> 1.1.6'
 gem 'qa', '~> 1.1.0'
 gem 'sprockets', '~> 2.12.4'  # locked
-gem 'rack-dev-mark', '~> 0.7.5'
+gem 'rack-dev-mark', '~> 0.7.8'
 
 # Deploy with Capistrano
 gem 'capistrano', '~> 3.8.1'

Gemfile.lock

@@ -287,9 +287,9 @@ GEM
       nokogiri (~> 1.6)
       rails (>= 4.2.0, < 6.0)
       rdf
-    rack (1.6.11)
-    rack-dev-mark (0.7.5)
-      rack (>= 1.1)
+    rack (1.6.13)
+    rack-dev-mark (0.7.8)
+      rack (>= 1.1, < 2.1)
     rack-test (0.6.3)
       rack (>= 1.0)
     rails (4.2.11.1)
@@ -490,7 +490,7 @@ DEPENDENCIES
   pry
   pry-byebug
   qa (~> 1.1.0)
-  rack-dev-mark (~> 0.7.5)
+  rack-dev-mark (~> 0.7.8)
   rails (~> 4.2.11)
   rails_autolink (~> 1.1.6)
   rake (~> 12.3.3)