Context object compatibility

[thekid]

We're missing the following properties:

• [x] logGroupName – The log group for the function, from: $_ENV['AWS_LAMBDA_LOG_GROUP_NAME'] ?? null
• [x] logStreamName – The log stream for the function instance, from: $_ENV['AWS_LAMBDA_LOG_STREAM_NAME'] ?? null

...as a difference to https://docs.aws.amazon.com/lambda/latest/dg/nodejs-context.html

[thekid]

memorySize should be named memoryLimitInMB

[thekid]

Implemented and released in https://github.com/xp-forge/lambda/releases/tag/v0.7.0