Fix Gemfile/Gemfile.lock

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Gemfile

@@ -6,7 +6,7 @@ group :development, :test do
   gem 'pry'
   gem 'rake'
   gem 'posix-spawn', "~> 0.3.6"
-  gem 'mime-types', "~> 2.6"
+  gem 'mime-types', ">= 1.16", "< 3"
   gem 'diff-lcs', "~> 1.1"
   gem 'mocha', "~> 0.13.2"
   gem 'coveralls', require: false

Gemfile.lock

 PATH
   remote: .
   specs:
-    gitlab-grit (2.8.0)
+    gitlab-grit (2.8.1)
       charlock_holmes (~> 0.6)
       diff-lcs (~> 1.1)
       mime-types (>= 1.16, < 3)
@@ -56,7 +56,7 @@ DEPENDENCIES
   coveralls
   diff-lcs (~> 1.1)
   gitlab-grit!
-  mime-types (~> 2.6)
+  mime-types (>= 1.16, < 3)
   mocha (~> 0.13.2)
   posix-spawn (~> 0.3.6)
   pry