Use Sinatra 2.2.* for Ruby greater or equal to 2.4.0

Author: kinow

Gemfile.lock

@@ -7,7 +7,7 @@ PATH
       rack (>= 2.2, < 4.0)
       rufus-scheduler (~> 3.6)
       sassc (~> 2.0)
-      sinatra (~> 2.0)
+      sinatra (~> 2.2)
       sinatra-contrib (~> 2.0)
       sprockets (~> 4.0)
       thin (~> 1.7)

smashing.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |s|
   if RUBY_VERSION < "2.4.0"
     s.add_dependency('sinatra', '= 2.0.4') 
   else
-    s.add_dependency('sinatra', '~> 2.0')
+    s.add_dependency('sinatra', '~> 2.2')
   end
   s.add_dependency('sinatra-contrib', '~> 2.0')
   s.add_dependency('thin', '~> 1.7')