Added IAM instance profile support for AWS credentials
Added IAM instance profile support for AWS credentials

The Fog gem already supports IAM instance profiles. This adds support
into the EBS cookbook recipe.

Closes #72

gouketsu/cookbook-elasticsearch,zzugg/cookbook-elasticsearch,michaeld/elasticsearch-cookbook,zzugg/cookbook-elasticsearch,zzugg/cookbook-elasticsearch,spuder/cookbook-elasticsearch,nbudin/cookbook-elasticsearch,gouketsu/cookbook-elasticsearch,gilt/cookbook-elasticsearch,bavardage/cookbook-elasticsearch,gilt/cookbook-elasticsearch,spuder/cookbook-elasticsearch,vacay/vcy-elasticsearch,nbudin/cookbook-elasticsearch,paulczar/cookbook-elasticsearch,gilt/cookbook-elasticsearch,spuder/cookbook-elasticsearch,gouketsu/cookbook-elasticsearch,nbudin/cookbook-elasticsearch,GemHQ/cookbook-elasticsearch,vacay/vcy-elasticsearch,vacay/vcy-elasticsearch