tests

tests(ci): add basic CI tests and fix POST requests bug #8

Job	Run time
test (16.x)	11s
test (18.x)	12s
examples (16.x, not_stringified_body)	14s
examples (16.x, print_event_context)	12s
examples (16.x, stringified_body)	12s
examples (16.x, upload_file_multipart)	10s
examples (16.x, with_callback)	9s
examples (16.x, with_event_components)	11s
examples (16.x, with_http_get)	13s
examples (16.x, with_http_post)	8s
examples (16.x, with_object)	9s
examples (16.x, with_promise)	8s
examples (18.x, not_stringified_body)	9s
examples (18.x, print_event_context)	1s
examples (18.x, stringified_body)	10s
examples (18.x, upload_file_multipart)	9s
examples (18.x, with_callback)	1s
examples (18.x, with_event_components)	1s
examples (18.x, with_http_get)	1s
examples (18.x, with_http_post)	1s
examples (18.x, with_object)	1s
examples (18.x, with_promise)	1s
	2m 44s

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