Update Rust documentation (1.14.0)

Fixes #550.

lib/docs/filters/rust/clean_html.rb

@@ -10,7 +10,7 @@ module Docs
           api
         end
 
-        css('.rusttest', 'hr').remove
+        css('.rusttest', '.test-arrow', 'hr').remove
 
         css('.docblock > h1').each { |node| node.name = 'h4' }
         css('h2.section-header').each { |node| node.name = 'h3' }

lib/docs/scrapers/rust.rb

@@ -1,7 +1,7 @@
 module Docs
   class Rust < UrlScraper
     self.type = 'rust'
-    self.release = '1.13.0'
+    self.release = '1.14.0'
     self.base_url = 'https://doc.rust-lang.org/'
     self.root_path = 'book/index.html'
     self.initial_paths = %w(