Move route methods to helpers object

Fixes #14

Adding the routes directly to the test class is problematic if a route
begins with "test", as the url method will be treated as a test method.
Defer these methods to a separate helpers object to avoid this.
Add mounted_helpers [closes #25]
Add Travis-CI support
Update minitest dependencies

Worried that newer versions of these libraries will only support Minitest 5.
Pin to these specific versions to avoid dependency hell.
Update manifest and gemspec
Update Rakefile

Deleting the rubyforge hoe plugin is no longer needed.