Include weave dns information in weave status

[awh]

Addresses #237 - Add weavedns status to weave status.

Sample output:

~/weave$ sudo ./weave status
weave router git-9eeec2fa4835
Encryption off
Our name is 7a:6e:b1:a9:28:4d (ubuntu-14)
Sniffing traffic on &{12 65535 ethwe 6e:54:91:56:f2:9a up|broadcast|multicast}
MACs:
Peers:
Peer 7a:6e:b1:a9:28:4d (ubuntu-14) (v0) (UID 17345352114913090227)
Routes:
unicast:
7a:6e:b1:a9:28:4d -> 00:00:00:00:00:00
broadcast:
7a:6e:b1:a9:28:4d -> []
Reconnects:

weave DNS git-6f57774d1516
Local domain weave.local.
Listen address :53
mDNS interface &{112 65535 ethwe ea:43:db:f3:c3:3d up|broadcast|multicast}
Fallback DNS config &{[10.0.2.3] [] 53 1 5 2}
Zone database:
2aca5f21b82b1898f7e9bb6919b77a56999e6c4b7c292f3f88c8cec3a7db72b7 10.2.1.4 waff.weave.local.
5962267f738d8db93d2b119968dc881014a82a30db57b96f5cb786fd911fc334 10.2.1.3 wiff.weave.local.
542a24da39383cf6ca64ca67dd7560c3d4ef145a04b1decc8cd5d082a17aa3db 10.2.1.2 pong.weave.local.
1226cbc0bee34c57373b65b63a42c6f47449e29388df2fd5ed7aebddf9fa0110 10.2.1.1 ping.weave.local.

Implementation notes:

• As per in-person discussion with @squaremo and @rade this is implemented by /status returning a human readable text/plain document to mirror the current router REST API
• Suggested HEAD optimisation has been omitted due to curl -X behaviour

[awh]

I've taken Gorilla mux out of this PR, will reintroduce it in a separate patch that covers the weave router too.

[awh]

Invite @inercia for review.

[awh]

Documentation update to follow shortly...

[inercia]

Everything looks good to me 👍

[awh]

@rade re: your other comments lost due to my force push:

iirc weave ps displays shorter container IDs. We should use the same length here.

weave ps relies on Docker, which I suspect is printing out max(12, shortest distinct container ID). Do you want me to just truncate to 12 chars or calculate shortest distinct prefix too?

try to use a relative link here.

I'm not sure this is possible as it's pointing to something outside of the site folder. Other such links in this document are absolute...

[rade]

I'm not sure this is possible as it's pointing to something outside of the site folder.

https://help.github.com/articles/relative-links-in-readmes/ - worth a try

Other such links in this document are absolute...

I don't think I put them there ;)

[awh]

Those relative links will work if you browse to the markdown documents via the github repository browser, but they will break once site is published to the gh_pages branch...