Merge tag '0.11' into develop

v0.11
Bugfix for to_string()
Make thread safe
Whitespace
Better marble string parser
Whitespace and comments
Bugfix: add missing import
Cleanup
Bugfix: no method called to_absolute
Make it possible to set custom Lock
Make thread safe
Cleanup
Added replay
Merge branch 'develop' of github.com:ReactiveX/RxPY into develop
Cleanup
Whitespace
New priorityqueue based on heapq
Cleanup
Added eventloopscheduler
Use python len()