Added tests for TTLs
Refactor GetFromStorage() to query for TTLs too
Added a little comment about an optimisation
Added a test to ensure bad TTL values don't break queries
Implement more efficient TTL querying

There's no need to hit etcd for every single key we need a TTL for. This is
the case when performing recursive queries, since we already have the keys containing
TTL data in the list of nodes, we just need to filter them out.

By sorting the list of keys first, we can do this in an iterative manor.
Add a test for first result in an etcd dir being a .ttl
Actually, that last commit was for solo records, _this_ is for dirs
Correct my new TTL tests:

- copy-pasted namespace invalidates the tests. Fail.
- Use TXT records, so that failures aren't hidden behind IP-parsing errors
Add a more complete test for directory TTL errs
Ack, that was silly. Properly compare txt content
Refactor TTL-node hunt to be less brittle
Merge pull request #23 from duedil-ltd/feature/record-ttls

Implement TTLs for records