#41 - scan on_subscribe should be const
Merge pull request #42 from kirkshoop/issue41

#41 - scan on_subscribe should be const
#39 - race on function static causes AV

This moves function statics to class statics. Side effect is that the
event_loop threads are started even if they are not used. A future
change might make event_loop thread creation lazy.
ignore apt errors
Merge pull request #43 from kirkshoop/issue39

#39 - race on function static causes AV
fix travis and workaround for libstd++ bug
Merge pull request #45 from kirkshoop/workaroundforhang

fix travis and workaround for libstd++ bug
Add zip operator including tests
Clang compilation fixes
Disable clang optimization that spoils value extracted from list.