etcdhttp: trim StoreKeysPrefix from error in serveKeys

It returns error messaage like this now:
'{"errorCode":100,"message":"Key not found","cause":"/1/pants","index":10}'

The commit trims '/1' prefix from cause field if exists.

This is a hack to make it display well. It is correct because all error causes
that contain Path puts Path at the head of the string.
Merge pull request #1396 from unihorn/185

etcdhttp: trim StoreKeysPrefix from error in serveKeys
Documentation/0.5: add api.md

- Update all of the ports to use the new IANA port numbers
- Update the stats section to talk about the id fields
- Remove mention of the modules
- Remove -L from all of the curl commands since it is no longer needed
- Point people at the clustering.md guide for the cluster APIs
Merge pull request #1393 from philips/0.5-docs2

Documentation/0.5: add api.md
proxy: retrieve ClientURLs from cluster

This is a simple solution to having the proxy keep up to date with the
state of the cluster. Basically, it uses the cluster configuration
provided at start up (i.e. with `-initial-cluster-state`) to determine
where to reach peer(s) in the cluster, and then it will periodically hit
the `/members` endpoint of those peer(s) (using the same mechanism that
`-cluster-state=existing` does to initialise) to update the set of valid
client URLs to proxy to.

This does not address discovery (#1376), and it would probably be better
to update the set of proxyURLs dynamically whenever we fetch the new
state of the cluster; but it needs a bit more thinking to have this done
in a clean way with the proxy interface.

Example in Procfile works again.