Feature: Provide a way to do arbitrary things between blocks

[devslash-paul]

There are times where between calls you'd like to do some organisation or changes. It'd be nice to be able to have an action take place when you know one set of calls have finished and the next are about to begin.

This could be something like saying "Finished X, doing Y".

This is better than new runHttp blocks as you'll keep auth and any session cookies