hamfisted addition of command-line option to add support for
backing up just a single org, instead of all orgs. intended
to simplify ec server migration scenarios where there may be
many orgs present but not involved in the current migration
effort.

skips backing up users and user_acls on the assumption that
they will already have been restored to the destination server.
Fix skip-pivotal option logic
Update banner to show that a backup directory is required.
Add password to key dump
Update ec_backup.rb

incorporating suggested changes
Merge pull request #31 from strickra/master

add support for backing up just a single org
Fix group uploads by topologically sorting.
Avoid monkey-patching Hash by creating a Chef::Tsorter helper class
Merge pull request #36 from opscode/ssd/topo-sort-actors

Fix group uploads by topologically sorting
Depend on ChefFS from Chef rather than knife-essentials.

This changes all requires to point at the version of ChefFS inside Chef
itself.  We also depends on Chef 11+.
Remove PATH reset code as it leads to errors in Chef 11.

It seems that setting the various _path variables to nil prevents
them from being generated automatically from chef_repo_path.

We depend on their automatic generation.
Restore path-clearing code using newer Chef::Config methods.
Chef ~> 11.8 required for fixes in chef_fs.

Specifically, older versions of Chef 11 fail when trying to create
already existing directories inside the backup.
Move path clearning inside begin/ensure block