I checked the error that you are facing and this arrives when you are using the Professional edition of Salesforce.


This REST API access feature is enabled by default for Unlimited, Enterprise, and Developer Editions. However, it is not available for the basic version of Professional Edition.

 


Read this for more info:
http://www2.sfdcstatic.com/ap/assets/pdf/datasheets/DS_SalesCloud_EdCompare.pdf

 

For more information about enabling API access for your Salesforce Organization please contact Salesforce.com support.