CF module should use the lambda's region as default

[HyperBrain]

Currently the CF integration uses the SERVERLESS_REGION variable that is not set by default. That means that you have to set it manually for each region.
As most users would use the lambda context's region it would be better to set this as default. Then serverless' environment variables would stay clean. Technically the lambda region can be retrieved from the AWS SDK.
An optional parameter could be added to CF.loadVars() to cover the remaining corner cases where you do not want to use the default.

[HyperBrain]

I did some investigations now how to retrieve the current region with help of the AWS-SDK.
Currently this functionality is only integrated in the Java AWS-SDK for EC2.
Technically they query the EC2MetaData from the global metadata service at "http://169.254.169.254" and retrieve the "/latest/dynamic/instance-identity/document" (see getEC2InstanceRegion() method).
I'm not really sure if this is also possible and when, if it's stable within the lambda's environment.
@ryansb @maxmadell Do you have any ideas/experience in that area?