Use controller's base path instead of constant name at controller test

Closes #1765
Use expanded path to request controller's content
add skipped failing erb test for #1785
fix skip position
Routing#process_path_for_parent_params should be a public method

Because this is used in the controller generator
use yield whenever possible
use flat_map whenever possible
clarify each_with_object usage
prefer #tr or #sub over gsub when possible
avoid parallel assignment if possible
Make the Mounter support the Rack application

Conflicts:
	padrino-core/lib/padrino-core/mounter.rb
Fix an exception that occurs when the free regex route exists

Fixes #1788
Merge pull request #1787 from padrino/support-rack-app

Make Padrino::Mounter support the Rack application
Merge pull request #1779 from padrino/more-descriptive-controller-test

Use controller's base path instead of constant name at controller test
allow Padrino::Rendering on stdlib ERB
add travis run for stdlib-erb
use stdlib ERB lazily if no erb gem was bundled
emulate basic Sinatra set for Padrino::Mailer