Add test to Marketo lead calls

This introduces 'node-replay', which allows us to capture actual API
calls to Marketo and replay it back to us in future test runs

UM-85
Merge pull request #3 from usermindinc/ak-add_leads_tests

Add test to Marketo lead calls
Do not include the response object in the promise

Having it is sometimes useful, but it results in huge logs when we log
the resulting object out.