Adding JSON logging as a function.

[tomgco]

This commit introduces a new method of logging from within AWS Lambda's.

It delegates to Bunyan and produces log messages in the structure defined below:

{
    "name": "aws-canary-lambda",
    "invokedFunctionArn": "arn:aws:lambda:eu-west-1:123456789:function:aws-canary-lambda:1",
    "traceableId": "some-id",
    "module": "where-i-am-from",
    "hostname": "magellanic",
    "version": "1",
    "pid": 25728,
    "level": 30,
    "msg": "hello in stdout",
    "time": "2016-05-06T11:48:44.207Z",
    "v": 0
}

As seen above this function also reads the current context of the lambda and populates some common fields to embelish logs with some added features, which could be indexed if sent to Elasticsearch.

[codecov-io]

Current coverage is 100%

Merging #31 into master will increase coverage by +n/a%

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[tomgco]

As a note, the dependency bunyan is 492KB on disk when it is installed with npm install --no-optional and 4.8MB when installed with all dependencies.

[tomgco]

Review with @plaenen, let's rename the attribute: module: String to either tags: Array or labels: Array by passing in an array to the constructor.

[jruts]

@tomgco looks good. Can you update the package version so we can npm publish after merging? Thanks!

[tomgco]

@tomgco looks good. Can you update the package version so we can npm publish after merging?

Thanks, updated the minor version number.