Support Locust 1.0+

[tortila]

Locust 1.0 was released recently, and from the changelog it looks like it has at least one breaking change that concerns Zelt (command line arguments).

Transformer with Locust 1.0+ support was released as alpha version, and will be soon released with all needed features (see: zalando-incubator/transformer#69).

Describe the solution you'd like.
Implement needed changes in Zelt to support Locust 1.0+, update example code and manifests.