Add a CLI Preview tool

[jasonLaster]

It'd be great if you could preview the changes that were going to be made.

A sample preview would look like:

53 Changes
5 CollectionView changes
10 ItemView changes

[fluxsaas]

you could use git status in your project directory..?

[jamesplease]

heh, true, @fluxsaas, but I think the point here is we could do better than that.

Grouping by type and presenting a single number for each type is a bit more useful than simply showing a list as the number of changed files grows.