* Fix: formatter try to evaluate the headers sym_links hash keys as string

Author: Jonathan Garay

lib/grape/middleware/formatter.rb

@@ -13,11 +13,11 @@ def default_options
           :parsers => {}
         }
       end
-      
+
       def headers
-        env.dup.inject({}){|h,(k,v)| h[k.downcase[5..-1]] = v if k.downcase.start_with?('http_'); h}
+        env.dup.inject({}){|h,(k,v)| h[k.downcase[5..-1]] = v if k.downcase.to_s.start_with?('http_'); h}
       end
-      
+
       def before
         fmt = format_from_extension || options[:format] || format_from_header || options[:default_format]
         if content_types.key?(fmt)
@@ -39,7 +39,7 @@ def before
           throw :error, :status => 406, :message => 'The requested format is not supported.'
         end
       end
-      
+
       def format_from_extension
         parts = request.path.split('.')
         extension = parts.last.to_sym
@@ -49,7 +49,7 @@ def format_from_extension
         end
         nil
       end
-      
+
       def format_from_header
         mime_array.each do |t|
           if mime_types.key?(t)
@@ -58,15 +58,15 @@ def format_from_header
         end
         nil
       end
-      
+
       def mime_array
         accept = headers['accept'] or return []
 
         accept.gsub(/\b/,'').scan(%r((\w+/[\w+.-]+)(?:(?:;[^,]*?)?;\s*q=([\d.]+))?)).sort_by { |_, q| -q.to_f }.map {|mime, _|
           mime.sub(%r(vnd\.[^+]+\+), '')
         }
       end
-      
+
       def after
         status, headers, bodies = *@app_response
         formatter = formatter_for env['api.format']