Remove Haml in favor of erb views

Update usages in the sinatra app

Remove haml files mentioned in the gemspec,
remove the haml gem and require, and bump the
gem version.

"rake" passes, and I tried in a rails 4 app
specifying this gem with the "path" option for
bundler, and the basic pages rendered OK

Related to https://github.com/ejschmitt/delayed_job_web/issues/40 and https://github.com/ejschmitt/delayed_job_web/issues/31