chore: Update example apps from nodejs6.10 to nodejs8.10 and add samp…

[carvantes]

Description of changes:
Upgrade several example apps from nodejs6.10 to nodejs8.10. Also, added a testEvent.json with a valid test event on each of them to make them easier to test with sam local invoke.
Most test events are taken from sam local generate-event

Description of how you validated changes:
sam local invoke -e testEvent.json ran successfully on all examples

The exceptions that cannot be tested that way are:

• s3-get-object, deployed with sam package/deploy and manually tested.
• microservice-http-endpoint, deployed with sam package/deploy and created a simple DDB table to manually test it

Checklist:

• Write/update tests. N/A, There are no actual tests for example apps, the added testEvent.json is useful for testing though
• make pr passes
• Update documentation. N/A, there are no docs to update

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #883 into master will decrease coverage by 0.78%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #883      +/-   ##
==========================================
- Coverage   95.32%   94.54%   -0.79%     
==========================================
  Files          69       67       -2     
  Lines        3789     2824     -965     
  Branches      831      508     -323     
==========================================
- Hits         3612     2670     -942     
+ Misses         96       81      -15     
+ Partials       81       73       -8

Impacted Files	Coverage Δ
samtranslator/yaml_helper.py	80% <0%> (-10%)	⬇️
...lator/plugins/application/serverless_app_plugin.py	80.15% <0%> (-3.33%)	⬇️
samtranslator/model/eventsources/push.py	88.73% <0%> (-3.13%)	⬇️
samtranslator/parser/parser.py	86.66% <0%> (-2.99%)	⬇️
samtranslator/model/__init__.py	96.85% <0%> (-1.26%)	⬇️
samtranslator/model/apigateway.py	96.32% <0%> (-0.72%)	⬇️
samtranslator/swagger/swagger.py	98.32% <0%> (-0.43%)	⬇️
samtranslator/intrinsics/actions.py	98.52% <0%> (-0.26%)	⬇️
samtranslator/model/sam_resources.py	96.09% <0%> (-0.25%)	⬇️
samtranslator/plugins/globals/globals.py	100% <0%> (ø)	⬆️
... and 5 more

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