Support Ember's new Router api: Added basePath / -b option which is used to calculate the relative path which is then added to the template name

The new router api from Ember is expecting template names which have a complete path, when using nested routes. This requires template names like 'website/users/user' instead of 'user' which is currently the templateName when such a template is precompiled.

This pull request enables a -b option which refers to the path which is stripped from the full-path of the template which is being compiled. The template name is then built from the stripped path + the filename itself (without the .handlebars).