Adding Elastic IP queries and binding.

0.1.4

Adding AssociateEipAddress()

improving key pair management

0.1.3

Improve key pair management.

fixing instance attributes.

0.1.2

Removing "id" from Credential. Completing Instance.

Adding public initialization to structures.

0.1.1

Adding public initilization

init

0.1.0

Appending more info of `AcsRequest()`