Record write acknowledgements

[2.1.0] - 2016-12-21

Features

• Record write acknowledgement. Records are now able to be set with an optional callback which will be called with any errors from storing the record in cache/storage #290

Enhancements

• Additional tests around presence and records #284 and #285
• Allow passing of node socket options into constructor #289

Bug Fixes

• Fix bug in JSON path when updating nested null values #281
• Adding check for undefined entries in single notifier #291