AWS Identity and Access Management (IAM) support.

This commit adds support for the following AWS IAM actions:

- CreateAccessKey
- CreateUser
- DeleteAccessKey
- DeleteUser
- DeleteUserPolicy
- GetUserPolicy
- ListAccessKeys
- ListUserPolicies
- ListUsers
- PutUserPolicy
- UpdateAccessKey
- UpdateUser

Added self to contributors.
Merge pull request #80 from abhinav/iam

AWS Identity and Access Management (IAM) support.