Coverage decreased (-0.3%) to 96.875% when pulling a3cdd94 on sunnylqm:patch-1 into 7d1865c on chimurai:master.

Please provide a description and test plan for this PR.

@chimurai for example

{
        path: '/proxy',
        target: 'http:/example.com',
        pathRewrite: () => ''
}

If I want to replace the whole path into an empty string, then it would complain "No rewritten path found"

Testing for a string should be safer.
This will better cope with 'garbage' returned by custom functions...
(Array's, Objects, undefined, etc...)

Coverage decreased (-0.3%) to 96.875% when pulling f597c1d on sunnylqm:patch-1 into 7d1865c on chimurai:master.

Can it be merged now @chimurai

Sorry for the late response.
Thanks for contributing!