Make pollingInterval configurable

[matteodem]

see http://info.meteor.com/blog/tuning-meteor-mongo-livedata-for-scalability

should replace the earlier reactive: false configuration in v1, see #65

• make the count polling interval configurable, see #556
• add docs regarding performance configuration (count interval ms config + pollingInterval config)

[frankapimenta]

Any news regarding this? :)

[matteodem]

No, I'm rather busy with work right now. Feel free to submit a PR if you have time.

[matteodem]

This is now configurable on engine level http://matteodem.github.io/meteor-easy-search/docs/engines/