Now we retrieve the git hash/branch from a git command.

Instead of inspecting the .git dir directly.  This means that the ember
app can be a sub directory of a git repo
Merge pull request #37 from achambers/better-git-hash

Improve how we retrieve the git hash and branch
Added assets config validator
Now deploy-assets command is using new config validator
Now deploy assets task works with new config getting methods
Added index config validator
Now deploy index command uses new config validator