return 404 if tag lookup failed

return 404 (via Sinatra 'halt') if no entries found for a tag lookup so that an automated query gets an error response code rather than having to parse the error message
remove sinatra/reloader from aws branch

sinatra/reloader reloads the code on every request: inappropriate for production usage
require './web_note_mongo'

need to use relative path in require statement for version of ruby installed on aws Ubuntu 12.04 instance
remove Gemfile & lock

aws instance has gems installed at the system level, rendering bundler spurious (and possibly harmful)
add config.ru