v0.8

• Add BatchSemaphore (#151)
• block_on now has one less thread switch point, which breaks schedules. (#155)
• ReplayScheduler::set_target_clock added (#156)
• Schedulers now receive references to Tasks instead of TaskIds (#156)
• Expose check_random_with_seed (#161)
• Make check_random optionally take a seed by providing the environment variable SHUTTLE_RANDOM_SEED (#161)
• Shuttle Explorer extension (#163).
• AnnotationScheduler and annotated schedule support added under feature "annotation" (#163)