Merge tag 'stevedore-0.8.0-beta.5' into develop

pallet-stevedore-0.8.0-beta.5
Updated version for next release cycle
Fix the 'group' keyword in bash
Throw error if *script-context* not set
Improve the 'group' keyword implementation in bash

This causes the grouping to output commands on separate lines, rather
than all in one line.
Updated project.clj, release notes and readme for 0.8.0-beta.6
Merge branch 'release/0.8.0-beta.6'