Tail remote logs live

Make 'lymph tail' able to connect and disconnect from service and they
come and go, and that by making lymph.core.services.Service class
implement an Observable interface, that the newly introduced class
RemoteTail will use to observe when services get added or removed,
and react by connecting and disconnecting from this later respectively.
Merge pull request #30 from mouadino/tail-follow

Tail remote logs live
Include ids for scheduled events to make schedule data unique
Fixed whitespace
Fixed connection loss errors with zookeeper discovery
Use print_function in cli commands
Removed obsolete broker service
Upgraded coverage dependency to lastest master (4.0)
Renamed iris to lymph in Makefile
Renamed installed_services to installed_interfaces
Added serial_event illustration
Merge pull request #25 from emulbreh/cleanup

Cleanup
Fix setup.py: install gevent from scratch for Python 3
Remove setup_requires, it isn't necessary
Merge pull request #32 from manisenkov/fix-setup-for-py3

Fix setup.py: install gevent from scratch for Python 3
Updated installation instruction in README: lymph is now pip installable