Serve more static assets (`apple-touch-icon.png`, ...?)

[dentarg]

The request to /apple-touch-icon.png ended up in PageController but it should not, discovered because the database connection failed when trying Fly (#402)

PG::ConnectionBad: PQconsumeInput() server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.

  from sequel/adapters/postgres.rb:171:in `exec'
  from sequel/adapters/postgres.rb:171:in `block in execute_query'
  from sequel/database/logging.rb:38:in `log_connection_yield'
  from sequel/adapters/postgres.rb:171:in `execute_query'
  from sequel/adapters/postgres.rb:159:in `block in execute'
  from sequel/adapters/postgres.rb:136:in `check_disconnect_errors'
  from sequel/adapters/postgres.rb:159:in `execute'
  from sequel/adapters/postgres.rb:528:in `_execute'
  from sequel/adapters/postgres.rb:344:in `block (2 levels) in execute'
  from sequel/adapters/postgres.rb:551:in `check_database_errors'
  from sequel/adapters/postgres.rb:344:in `block in execute'
  from sequel/connection_pool/threaded.rb:92:in `hold'
  from sequel/database/connecting.rb:269:in `synchronize'
  from sequel/adapters/postgres.rb:344:in `execute'
  from sequel/dataset/actions.rb:1142:in `execute'
  from sequel/adapters/postgres.rb:647:in `fetch_rows'
  from sequel/dataset/actions.rb:993:in `with_sql_each'
  from sequel/dataset/actions.rb:1003:in `with_sql_first'
  from sequel/dataset/actions.rb:758:in `single_record!'
  from sequel/dataset/actions.rb:245:in `first'
  from sequel/model/plugins.rb:33:in `first'
  from sequel/model/base.rb:409:in `find'
  from lib/controllers/page_controller.rb:110:in `block in <class:PageController>'
  from sinatra/base.rb:1684:in `call'
  from sinatra/base.rb:1684:in `block in compile!'
  from sinatra/base.rb:1002:in `block (3 levels) in route!'
  from sinatra/base.rb:1020:in `route_eval'
  from sinatra/base.rb:1002:in `block (2 levels) in route!'
  from sinatra/base.rb:1051:in `block in process_route'
  from sinatra/base.rb:1049:in `catch'
  from sinatra/base.rb:1049:in `process_route'
  from sinatra/base.rb:1000:in `block in route!'
  from sinatra/base.rb:997:in `each'
  from sinatra/base.rb:997:in `route!'
  from sinatra/base.rb:1121:in `block in dispatch!'
  from sinatra/base.rb:1092:in `catch'
  from sinatra/base.rb:1092:in `invoke'
  from sinatra/base.rb:1116:in `dispatch!'
  from sinatra/base.rb:932:in `block in call!'
  from sinatra/base.rb:1092:in `catch'
  from sinatra/base.rb:1092:in `invoke'
  from sinatra/base.rb:932:in `call!'
  from sinatra/base.rb:921:in `call'
  from rack/flash.rb:124:in `call'
  from rack/protection/xss_header.rb:20:in `call'
  from rack/protection/path_traversal.rb:18:in `call'
  from rack/protection/json_csrf.rb:28:in `call'
  from rack/protection/base.rb:53:in `call'
  from rack/protection/base.rb:53:in `call'
  from rack/protection/frame_options.rb:33:in `call'
  from rack/logger.rb:17:in `call'
  from rack/common_logger.rb:38:in `call'
  from sinatra/base.rb:261:in `call'
  from sinatra/base.rb:254:in `call'
  from rack/head.rb:12:in `call'
  from sinatra/base.rb:219:in `call'
  from sinatra/base.rb:1995:in `call'
  from sinatra/base.rb:1554:in `block in call'
  from sinatra/base.rb:1770:in `synchronize'
  from sinatra/base.rb:1554:in `call'
  from rack/urlmap.rb:74:in `block in call'
  from rack/urlmap.rb:58:in `each'
  from rack/urlmap.rb:58:in `call'
  from rack/static.rb:161:in `call'
  from rack/session/abstract/id.rb:266:in `context'
  from rack/session/abstract/id.rb:260:in `call'
  from rack/ssl-enforcer.rb:52:in `call'
  from raven/integrations/rack.rb:51:in `call'
  from puma/configuration.rb:268:in `call'
  from puma/request.rb:89:in `block in handle_request'
  from puma/thread_pool.rb:343:in `with_force_shutdown'
  from puma/request.rb:88:in `handle_request'
  from puma/server.rb:430:in `process_client'
  from puma/server.rb:233:in `block in run'
  from puma/thread_pool.rb:150:in `block in spawn_thread'