Update ruby-commander to 4.1.5.

=== 4.1.5 / 2013-08-11

* Prevent deprecation warning when loaded in a Rails 4 environment (#58)

=== 4.1.4 / 2013-07-21

* Improve help formatting for multiline program and command descriptions
* Add ability to set speaking rate (@kethomassen)
* Clean up examples in docs (@parkr)

(taca)