Some minor cleanups in dep_spec.
Add new dep counter helpers that use expectations instead of the yield counter hack.
Reimplement the met?/meet counter dep specs using the should_receive counter helpers.
Reimplement deps_spec using the should_receive counter helpers.
Update the 'already met' tree in deps_spec to match the others.
Inline the 'already met?' met? specs in deps_spec.
Check the trees' top-level return values in deps_spec instead of using a separate spec.
Remove old counter dep helpers, which are unused now.
Tweak and reword the dep counting specs.
add xsecs spec
Merge pull request #264 from ministryofcomputation/master

tests for xsecs
Merge branch 'refactor-dep-specs'
Remove removed! methods from b8ad6d1.
Remove vestigal result_message from Dep (gone with #met/#unmet logging helpers).
Collapse #run_met_task into #process_met_task now some unused logging is removed.
Collapse #process_met_task into #process_self -- it's not required anymore.
Rename Dep#process_task to #invoke, to match DepDefiner.
Extract meeting logic from #process_self into #meet_dep, which mirrors #process_tree.
Rename the methods that handle the met/meet logic.
Merge branch 'met-meet-refactor'