events: add codebuild and codedeploy state-change event types

[roberth-k]

Adds the following CloudWatch event types:

• events.CodeBuildEvent (detail types: "CodeBuild Build State Change", "CodeBuild Build Phase Change")
• events.CodeDeployEvent (detail types: "CodeDeploy Deployment State-change Notification", "CodeDeploy Instance State-change Notification")

Tests based on examples sourced from AWS documentation.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-io]

Codecov Report

Merging #213 into master will decrease coverage by 1.33%.
The diff coverage is 44.82%.

@@            Coverage Diff             @@
##           master     #213      +/-   ##
==========================================
- Coverage   75.88%   74.55%   -1.34%     
==========================================
  Files          18       20       +2     
  Lines         647      676      +29     
==========================================
+ Hits          491      504      +13     
- Misses        115      127      +12     
- Partials       41       45       +4

Impacted Files	Coverage Δ
events/duration.go	44.44% <44.44%> (ø)
events/codebuild.go	45.45% <45.45%> (ø)

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[bmoffatt]

confirmed test data is copy-paste from the docs, nice! Thanks for the contribution!