* Update DNSimple-go to 0.61
This adds support for contexts, exports all return values, Adds ZoneRecordAttributes to fix support for blank record names.
* Add UserAgent to client
* Update Integration test for DNSimple
We now support Empty TXT, however we do not support Null MX yet.
* Bump to dnsimple-go 0.62 & use dnsimple.String()