First pass at Chef Solo provisioner.
Make JSON attributes work with real JSON!
Rename configuration `cookbook_paths` to `cookbooks_paths` to
conform to Vagrant wording.
Remove configuration `cookbook_path` to simplify some things.
Implement `avoid_sudo` configuration option.
Implement `skip_install` configuration to skip Chef installation.
Remove errant die statement.
Rename configuration `avoid_sudo` to `prevent_sudo`
Merge remote-tracking branch 'upstream/master' into provisioner-chef-solo

Conflicts:
	config.go

Add the chef-solo provisioner back to config.go.
Fix import path for chef-solo provisioner.
Add basic test file for provisioner-chef-solo.
Merge remote-tracking branch 'upstream/master' into provisioner-chef-solo
Improve logging.
Correct behavior for undefined recipe list.
Correct package name to upstream repo.
Remove redundant code and clean up some string concatenation.
Clean up Say statements.
Remove debugging statement.
builder/amazon: add block device mappings [GH-90]
website: document the amazon block device mappings
Update CHANGELOG: amazon block device mappings
common: Add new StepDownload to DRY up downloads
builder/virtualbox: switch download guest additions to use new common
builder/virtualbox: remove unused function
builder/vmware: switch to common download step