Prepare for 1.8.0 release 

1.7.1 (cloudant#178) 

Merge pull request cloudant#164 from glynnbird/issue163 1.6.2 - fix issue cloudant#163

Merge pull request cloudant#162 from glynnbird/1.6.1 dependency to cloudant-nano

Merge pull request cloudant#161 from glynnbird/prelease 1.6.0

Merge pull request cloudant#153 from glynnbird/promisesissues Promisesissues

Merge pull request cloudant#150 from glynnbird/plugin Plugin support

Bulk get and geospatial support 

Normal Nano dependency