Generate packages with cpack on Travis

[c42f]

Start of an attempt to get OSX packages working.

[c42f]

Looks like this will be a time sink. Some useful search results for later:

https://github.com/sgerbino/table/blob/d3d76886b69e104dce82f2292bbb0aee91d09ff9/.travis.yml https://github.com/search?utf8=%E2%9C%93&q=+cpack+-G+DragNDrop+travis&type=Code

May alternatively need cpack -G Bundle, or cpack -G PackageMaker...