Split output to separate module / library

Is your feature request related to a problem? Please describe. The roll output, that returns the string version of the roll log, is currently built in to the individual classes and is not easily changeable. It could be helpful if the output was built as a separate module, so that it can be easily swapped out for a different output type. This would enable easier modification of the output and allow things like HTML output.

Describe the solution you'd like Move the output functionality into it's own set of classes that can handle the various objects that need to be output.

It may be beneficial for this to be it's own library, rather than built in to the dice roller itself. The alternative is to simply build it inside the library as it's own set of modules.