Adds support for Amazon Elastic Load Balancer (ELB) logs

[arithmetric]

Adds support for Amazon Elastic Load Balancer (ELB) logs from Classic Load Balancer (using the formatELBv1 handler) or Application Load Balancer (using the formatELBv2 handler).

ELB access logs documentation:

• https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/access-log-collection.html
• https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-access-logs.html

An example implementation for parsing Classic Load Balancer logs and shipping them via TCP would use:

var shipper = require('lambda-stash');

exports.handler = function(event, context, callback) {
  var config = {
    tcp: {
      host: 'data.example.com',
      port: '10000'
    },
    string: {
      prefix: `token `,
    },
    mappings: [
      {
        bucket: 'elb-classic-logs',
        processors: [
          'parseSpaces',
          'formatELBv1',
          'convertString',
          'shipTcp'
        ],
      }
    ]
  };
  shipper.handler(config, event, context, callback);
};

Resolves #3.

[coveralls]

Coverage remained the same at 100.0% when pulling 9306619fe702555bb640f8a4873b3f010102bfb3 on add_elb_support into edc99f1c1e44f047753b3530617b6795d3216306 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9306619fe702555bb640f8a4873b3f010102bfb3 on add_elb_support into edc99f1c1e44f047753b3530617b6795d3216306 on master.