App upgrade/update commands or update README

[MatthewHager]

Now that this project uses submodules, it is necessary to not only check the base project for updates via git pull but also the submodules via git submodule update --init --recursive. This needs full documentation in the README but also it would be nice if this had an alias or command in valkyrie such as drush valkyrie upgrade which would upgrade everything if upgrades are available.

[ergonlogic]

Presumably we want users to be able to install Valkyrie via drush dl valkyrie, in which case I'd hope that the d.o packaging scripts would recursively clone the submodules. That said, having a way to switch to using git, and allowing for self-updating is certainly interesting.

[RealLukeMartin]

Proposed solution for this: #52

[ergonlogic]

I'd like to see this in 0.5.0, if that pull request is ready to go.

[RealLukeMartin]

Still need to refactor and implement the things you suggested on this PR #52, it got put on the back burner because of other projects, but I can work on it this week and put another PR in.

[ergonlogic]

Ok, it'd be nice as a future enhancement.