buildModels framework

This pull request updates the Dev branch to be in line with the master from my last PR and then it adds a new function `buildModels` and some utilities that allow the user to construct a list of models that is able to be ensembled either by specifying a list of methods (and accepting some of `caret`'s good default tuning parameters) or by specifying a `tuneList` as suggested in  issue #2. 

There is still some work to do -- I think we need to store additional attributes and allow further attributes to be passed, plus clean this up. But, it's a good start for this framework, and it should work. 

Some rudimentary tests, not yet in the `testthat` format, are also included.