If the length isn't `36`, return `false` immediately before firing up
the regexp engine.

Assuming the following output from a consul agent:

```
==> Consul agent running!
           Version: 'v0.7.3-43-gc5e140c-dev (c5e140c+CHANGES)'
           Node ID: '40e4a748-2192-161a-0510-9bf59fe950b5'
         Node name: 'myhost'
```

it is now possible to lookup nodes by their Node Name or Node ID, or a
prefix match of the Node ID, with the following caveats re: the prefix
match:

1) first eight digits of the Node ID are a required minimum (eight was
   chosen as an arbitrary number)
2) the length of the Node ID must be an even number or no result will be
   returned.

```
% dig @127.0.0.1 -p 8600 myhost.node.dc1.consul.
myhost.node.dc1.consul.	0	IN	A	127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a748-2192-161a-0510-9bf59fe950b5.node.dc1.consul.
40e4a748-2192-161a-0510-9bf59fe950b5.node.dc1.consul. 0	IN A 127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a748.node.dc1.consul.
40e4a748.node.dc1.consul. 0	IN	A	127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a74821.node.dc1.consul.
40e4a74821.node.dc1.consul. 0	IN	A	127.0.0.1
% dig @127.0.0.1 -p 8600 40e4a748-21.node.dc1.consul.
40e4a748-21.node.dc1.consul. 0	IN	A	127.0.0.1
```

…e IDs.

…hes.

…ookup returned nil.

Add a TODO to note where a future point of logging should occur once a
logger is present.

lookup returned nil.

Add a TODO to note where a future point of logging should occur once a
logger is present and a few additional comments to explain the program
flow.