Documentation: remove "token" from discovery docs

It was a bit confusing how the term "token" was overriden in various ways in this doc. Clean it up by referring to it as a discovery URL.

Documentation/cluster-discovery.md

@@ -13,11 +13,11 @@ Please note - at least 3 nodes are required for [cluster availability][optimal-c
 
 ## Using discovery.etcd.io
 
-### Create a Token
+### Create a Discovery URL
 
-To use the discovery API, you must first create a token for your etcd cluster. Visit [https://discovery.etcd.io/new](https://discovery.etcd.io/new) to create a new token.
+To use the discovery API, you must first create a unique discovery URL for your etcd cluster. Visit [https://discovery.etcd.io/new](https://discovery.etcd.io/new) to create a new discovery URL.
 
-You can inspect the list of peers by viewing `https://discovery.etcd.io/<token>`.
+You can inspect the list of peers by viewing `https://discovery.etcd.io/<cluster id>`.
 
 ### Start etcd With the Discovery Flag
 
@@ -26,10 +26,10 @@ Specify the `-discovery` flag when you start each etcd instance. The list of exi
 Here's a full example:
 
 ```
-TOKEN=$(curl https://discovery.etcd.io/new)
-./etcd -name instance1 -peer-addr 10.1.2.3:7001 -addr 10.1.2.3:4001 -discovery $TOKEN
-./etcd -name instance2 -peer-addr 10.1.2.4:7001 -addr 10.1.2.4:4001 -discovery $TOKEN
-./etcd -name instance3 -peer-addr 10.1.2.5:7001 -addr 10.1.2.5:4001 -discovery $TOKEN
+URL=$(curl https://discovery.etcd.io/new)
+./etcd -name instance1 -peer-addr 10.1.2.3:7001 -addr 10.1.2.3:4001 -discovery $URL
+./etcd -name instance2 -peer-addr 10.1.2.4:7001 -addr 10.1.2.4:4001 -discovery $URL
+./etcd -name instance3 -peer-addr 10.1.2.5:7001 -addr 10.1.2.5:4001 -discovery $URL
 ```
 
 ## Running Your Own Discovery Endpoint
@@ -37,10 +37,10 @@ TOKEN=$(curl https://discovery.etcd.io/new)
 The discovery API communicates with a separate etcd cluster to store and retrieve the list of peers. CoreOS provides [https://discovery.etcd.io](https://discovery.etcd.io) as a free service, but you can easily run your own etcd cluster for this purpose. Here's an example using an etcd cluster located at `10.10.10.10:4001`:
 
 ```
-TOKEN="testcluster"
-./etcd -name instance1 -peer-addr 10.1.2.3:7001 -addr 10.1.2.3:4001 -discovery http://10.10.10.10:4001/v2/keys/$TOKEN
-./etcd -name instance2 -peer-addr 10.1.2.4:7001 -addr 10.1.2.4:4001 -discovery http://10.10.10.10:4001/v2/keys/$TOKEN
-./etcd -name instance3 -peer-addr 10.1.2.5:7001 -addr 10.1.2.5:4001 -discovery http://10.10.10.10:4001/v2/keys/$TOKEN
+URL="http://10.10.10.10:4001/v2/keys/testcluster"
+./etcd -name instance1 -peer-addr 10.1.2.3:7001 -addr 10.1.2.3:4001 -discovery $URL
+./etcd -name instance2 -peer-addr 10.1.2.4:7001 -addr 10.1.2.4:4001 -discovery $URL
+./etcd -name instance3 -peer-addr 10.1.2.5:7001 -addr 10.1.2.5:4001 -discovery $URL
 ```
 
 If you're interested in how to discovery API works behind the scenes, read about the [Discovery Protocol](https://github.com/coreos/etcd/blob/master/Documentation/discovery-protocol.md).