Merge pull request #106 from merencia/v2.0.0

New Features:

• Added timezone support using tz-offset;
• Provide a function getStatus to retrive the task current status;
• Allows task functions to return a promise, node-cron hanldes that;

Depreciation:

• ImmediateStart: ImmediateStart is removed, and replaced by an options param. The same behavior is allowed by the option scheduled;