addCommand refactoring.
Update checkDescriptor method.

Check if descriptor is an object first.
Fix path resolution.
Fix sandbox path resolve.
Add two custom Error types.
Typing error with command name and severity level.
Merge branch 'master' of github.com:Techniv/node-command-io

Conflicts:
	tests/commandio-sandbox.js
Refactor the internal command management.
Prepare comming of next features.
Merge branch 'master' of github.com:Techniv/node-command-io
Add unit test + fix command error
Fix unit test.
Sandbox console width.
Fix exception on unknow command.
Fix checkDescriptor implementation.
[TDD] create unit test to error management
Exception management
Update readme and exemple.
Update README.md
Update readme
Update version number to alpha release.