v0.6.1

• Add feature to tag tasks (#98)
• Add scheduler to check for uncontrolled nondeterminism (#96, #97)
• Support spurious wakeups for thread::park (#101)
• Support different leaders when sync::Barrier is reused (#102)
• Make {Mutex, Condvar, RwLock}::new const (#106)
• Improve tracing spans (#99)
• Fix spurious deadlocks with FuturesUnordered (#105)
• Split schedule output over multiple lines (#103)
• Bump futures dependency (#107)