Bump Sinatra (2.0) and ActiveSupport (5.1)

Gemfile.lock

@@ -1,12 +1,12 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (5.0.2)
+    activesupport (5.1.0)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (~> 0.7)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    backports (3.7.0)
+    backports (3.8.0)
     better_errors (2.1.1)
       coderay (>= 1.0.0)
       erubis (>= 2.6.6)
@@ -35,6 +35,7 @@ GEM
     mini_portile2 (2.1.0)
     minitest (5.10.1)
     multi_json (1.12.1)
+    mustermann (1.0.0)
     nokogiri (1.7.1)
       mini_portile2 (~> 2.1.0)
     options (2.3.2)
@@ -45,24 +46,25 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.8.1)
       slop (~> 3.4)
-    rack (1.6.5)
-    rack-protection (1.5.3)
+    rack (2.0.1)
+    rack-protection (2.0.0)
       rack
     rack-test (0.6.3)
       rack (>= 1.0)
     rake (12.0.0)
     rr (1.2.0)
     sass (3.4.23)
-    sinatra (1.4.8)
-      rack (~> 1.5)
-      rack-protection (~> 1.4)
-      tilt (>= 1.3, < 3)
-    sinatra-contrib (1.4.7)
+    sinatra (2.0.0)
+      mustermann (~> 1.0)
+      rack (~> 2.0)
+      rack-protection (= 2.0.0)
+      tilt (~> 2.0)
+    sinatra-contrib (2.0.0)
       backports (>= 2.0)
       multi_json
-      rack-protection
-      rack-test
-      sinatra (~> 1.4.0)
+      mustermann (~> 1.0)
+      rack-protection (= 2.0.0)
+      sinatra (= 2.0.0)
       tilt (>= 1.3, < 3)
     slop (3.6.0)
     sprockets (3.7.1)

lib/app.rb

@@ -305,7 +305,7 @@ class App < Sinatra::Application
     CODE
   end
 
-  get %r{\A/feed(?:\.atom)?\z} do
+  get %r{/feed(?:\.atom)?} do
     content_type 'application/atom+xml'
     settings.news_feed
   end
@@ -325,7 +325,7 @@ class App < Sinatra::Application
     'codeigniter~3.0' => 'codeigniter~3'
   }
 
-  get %r{\A/([\w~\.%]+)(\-[\w\-]+)?(/.*)?\z} do |doc, type, rest|
+  get %r{/([\w~\.%]+)(\-[\w\-]+)?(/.*)?} do |doc, type, rest|
     doc.sub! '%7E', '~'
 
     if DOC_REDIRECTS.key?(doc)