Implement authentication service
Create credential store

The credential is stored in a file called `credentials.json`, side by side
with the binaries.
Run login before sync command
Ignore NCrunch folder
Include authentication token in every request to the Gallery
Merge pull request #12 from vtex/feature/authentication

Authentication
Release 0.2.0-beta
Rename class 'SyncVerbObtions'
Get the account name in the configuration file

Fixes #9
Use root folder instead subfolder to sync account

Fixes #8