chore: work in progress

Migrate test execution to AVA from tap.
This is necessary because tap has some
unresolved issue that make the test
cases flaky and tape lacks features
regarding being able to support code
coverage and Typescript compilation
at the same time. Using AVA fixes both
of those shortcomings.

Fixes hyperledger-cacti#238

Signed-off-by: Peter Somogyvari <peter.somogyvari@accenture.com>