In order to authenticate against protected endpoints, e.g.
```
export NOMAD_ADDR=https://$USER:$PASSWORD@nomad.example.net
nomad status
```
Instead of adding username and password to `api.Config`, this is a
rather simple change to the request handler code that passes along any
basic auth information.
* Reverted changes to get methods
* Added prefix query parameter
* Updated node status to use prefix based searching
* Fixed tests
* Removed truncation logic
