Dev

This is a big PR before the next PR. The goal here is to add the `caretList` and `buildModels` functionality to allow the user to generate a list of caret objects to be ensembled simply from the names of the methods. There are also some functions to summarize the results of ensembling. 

The next PR will move the documentation to `roxygen3` and fill in as much documentation as possible for all of the functions. The goal will be to eventually merge this `Dev` branch into `master` and consider the package feature complete for 2-class classification and for regression models. New features will be then added in the `Dev` branch moving forward.