Switch from Hanna to YARD.

* hanna has broken dependencies all the time
* we have a .yardopts file already for rubydoc.info
* just compare the rake tasks
* README has a TOC

This would also allow using YARD's doc tagging system at some point in the
future. Rakefile is still usable even if YARD is not installed.

.yardopts

@@ -1,2 +1,3 @@
 --readme README.rdoc
 --title 'Sinatra API Documentation'
+'lib/**/*.rb' - '*.rdoc'

Rakefile

@@ -48,25 +48,7 @@ end
 
 desc 'Generate RDoc under doc/api'
 task 'doc'     => ['doc:api']
-
-task 'doc:api' => ['doc/api/index.html']
-
-file 'doc/api/index.html' => FileList['lib/**/*.rb', 'README.*'] do |f|
-  require 'rbconfig'
-  hanna = RbConfig::CONFIG['ruby_install_name'].sub('ruby', 'hanna')
-  rb_files = f.prerequisites
-  sh(<<-end.gsub(/\s+/, ' '))
-    #{hanna}
-      --charset utf8
-      --fmt html
-      --inline-source
-      --line-numbers
-      --main README.rdoc
-      --op doc/api
-      --title 'Sinatra API Documentation'
-      #{rb_files.join(' ')}
-  end
-end
+task('doc:api') { sh "yardoc -o doc/api" }
 CLEAN.include 'doc/api'
 
 # README ===============================================================