Add option for custom base path

[krsyoung]

The purpose of this code is to support #78 which needs a way to specify a custom base path when running redmon from within Thin.

The common use case for this is to serve redmon from behind a frontend web proxy (currently the assets won't load). This code provides a new command line option that can be used as follows:

bin/redmon --base-path /redmon

This will run the Thin server and serve the content up at http://localhost:4567/redmon. For those running Docker, this will work very nicely with an Image like: https://hub.docker.com/r/vieux/redmon/

Comments & improvements welcomed!

[coveralls]

Coverage decreased (-4.9%) to 84.0% when pulling 5bb7eee on krsyoung:add_proxy_option into 9b1a310 on steelThread:master.

[coveralls]

Coverage decreased (-4.9%) to 84.0% when pulling 5bb7eee on krsyoung:add_proxy_option into 9b1a310 on steelThread:master.

[steelThread]

It would be (I need to look to make sure) more efficient if an instance of Redmon::App was constructed outside and then referenced by the block.

app = Redmon::App.new
map base_path do
  run app
end

or if you want to module scope the instance

map base_path do
  run @@app ||= Redmon::App.new
end

thoughts?

[krsyoung]

Hey @steelThread thanks for the feedback! I went with the first option for now and tested things (no issue). I also made a change to switch the default base_path to '' vs '/' as it was a little annoying to see the extra trailing slash all of the time when not needed.

Let me know what you think! Thanks

[coveralls]

Coverage decreased (-5.4%) to 83.444% when pulling 4c0deea on krsyoung:add_proxy_option into 9b1a310 on steelThread:master.

[steelThread]

@krsyoung - lgtm.