Trying to use the Sinatra-Spreadsheet library to deliver spreadsheets from Sinatra requests

app.rb

# Taken directly from README example
get '/' do
    response['Content-Disposition'] = "attachment; filename=yourtemplate.xls"
    content_type 'application/excel'

    spreadsheet :yourtemplate
end

config.ru

require 'rubygems'
require 'bundler/setup'
require 'sinatra/spreadsheet'
Bundler.require
require './app'
run Sinatra::Application

errors.txt

NameError at /
uninitialized constant Spreadsheet
file: spreadsheet.rb location: evaluate line: 33

Gemfile

source 'https://rubygems.org'

gem 'sinatra'
gem 'sinatra-spreadsheet',
    :require => 'sinatra/spreadsheet',
    :git     => 'git://github.com/sycobuny/sinatra-spreadsheet.git'

yourtemplate.spreadsheet

# Taken directly from README example
worksheet = workbook.create_worksheet(:name => 'My First Worksheet')
worksheet.row(0).concat(%w(Question Answer))
worksheet.row(1).concat(["Isn't writing spreadsheets cool?", "Yes"])