Allow to add a lambda function to more than one cloudfront distribution

[jjchiw]

Issue: #2

myHandler:
    name: 'myHandler-origin-request'
    handler: handler.main
    memorySize: 128
    timeout: 1
    lambdaAtEdge:
        - distribution: 'distribution1'
           eventType: 'origin-request'
        - distribution: 'distribution2'
           eventType: 'origin-request'

myHandler1:
    name: 'myHandler1-origin-request'
    handler: handler.main
    memorySize: 128
    timeout: 1
    lambdaAtEdge:
          distribution: 'distribution3'
           eventType: 'origin-request'

Track: https://github.com/silvermine/serverless-plugin-cloudfront-lambda-edge/pull/3

[coveralls]

Coverage decreased (-0.09%) to 5.464% when pulling fdab74cca77e432692e8aba109f2c701aba30507 on jjchiw:allow-to-add-a-lambda-function-to-more-than-one-cloudfront into 279b8014b981bfafac18b73e579cca992bc78287 on silvermine:master.

[jthomerson]

This will be covered by !13 in v2.0 of the plugin.