Update transitive transaction tests to reflect trust-graph specification

[ana0]

After PR CirclesUBI/circles-core#24 in the circles-api repo is merged, core tests should be added to reflect the test cases in the specification notes

The closest thing we have to e2e/integration tests is in the core tests, therefore I think this may make most sense here

[adzialocha]

We've decided to move the tests into circles-api as it will be more thorough to actually test against the edges.json contents. Going throught the circles-core we would only be able to test if a transaction succeeded or not which covers parts of what we want to test but not everything.

Also, the test setup in circles-api is not far: A mocked graph exists and we can mock the blockchain with ganache-core, the indexing methods in the api can be called directly.

Related PR: #49