You'd usually host on Heroku but when first getting the hang of things it's handy to test locally, especially while making look and feel changes or testing a new release of the Gem.

To get this going follow the Heroku process and make your GemFile, Gemfile.lock, config.ru and config files. Then simply run the following:

If you've made changes like require a new version of the travlrmap Gem you need to update the bundle:

$ bundle update
Fetching gem metadata from http://rubygems.org/...........
Using builder (3.2.2)
Using bundler (1.2.1)
Using gli (2.12.2)
Using multi_json (1.10.1)
Using multi_xml (0.5.5)
Using httparty (0.11.0)
Using json (1.8.2)
Using nokogiri (1.5.2)
Using rack (1.5.2)
Using rack-protection (1.5.3)
Using ruby_kml (0.1.7)
Using tilt (1.4.1)
Using sinatra (1.4.5)
Using travlrmap (1.0.0)
Your bundle is updated! Use `bundle show [gemname]` to see where a bundled gem is installed.

After that run:

$ bundle exec rackup
[2015-01-10 11:41:53] INFO  WEBrick 1.3.1
[2015-01-10 11:41:53] INFO  ruby 1.8.7 (2013-06-27) [x86_64-linux]
[2015-01-10 11:41:53] INFO  WEBrick::HTTPServer#start: pid=1648 port=9292

Now browse to your host port 9292 and you should see your local copy running. The bundle update step is only needed if you changed your Gemfile or the first time.