Add erlcloud

This didn't seem to compile erlcloud when I tried to test it and I am wondering if it is not running the rebar.config.script file.  Can you check this to see if it is ok?  If it isn't, perhaps a fork should be added to avoid the need to use a rebar.config.script file.  The erlcloud repository is a common dependency for client usage of Amazon EC2, S3, SQS, SimpleDB, Mechanical Turk, ELB.  I am adding it for the [cloudi_core](https://hex.pm/packages/cloudi_core) package, since cloudi_core depends on erlcloud for ec2 node discovery.