Custom tsuru.yml name

[guestisp]

Please add support to define custom tsuru.yml file name.

In some environments (like ours) an application yml config already exists to configure our services, would be better to use the same file for app configuration insted creating two different file (for example, our application.yml and tsuru.yml)

As all platform extents the base-platform, this configuration should be defined in base platform, by using an env variable or similiar.

For example:

export APP_CONFIG=application.yml

if APP_CONFIG is set, all platform should try to use that file as configuration file. If missing, standard tsuru.yml should be used.