feature request: .list-striped

Created by: exige81

Looking to add a list-striped class that is similar to table-striped to create a little more visual distinction between list-group-items. This is especially helpful on wider lists. Switching to a single column table to use table-striped isn't really semantically correct.

Sample codepen here: https://codepen.io/anon/pen/JOdBGG

Unfortunately this starts to fall apart when combined with other styles such as .active or the contextual classes..

If it's acceptable that a list-group-striped class doesn't play well with other list-group styles, I could submit a PR for this, otherwise perhaps someone with more expertise can provide a more elegant solution.