Support mocha parallel

[cgewecke]

This might be possible by setting an afterAll mocha root hook via require in the mocha config. The hook will write the processes' gasData to cache. Then, coming out of TASK_TEST we

• look in cache for files with the right title (like "hhgr.randomnumber.json")
• load and merge
• delete cached
• render

Questions

• is it safe to append/rewrite mocha require via the config? (Can you even?)