Added an example to ipfs id

I was super confused how to use the `-f` flag. This helped, but I had to go into
the test files to find it. Added it here.

License: MIT
Signed-off-by: Richard Littauer <richard.littauer@gmail.com>

core/commands/id.go

@@ -47,6 +47,10 @@ ipfs id supports the format option for output with the following keys:
 <pver>: protocol version
 <pubkey>: public key
 <addrs>: addresses (newline delimited)
+
+Example:
+
+		$ ipfs id Qmece2RkXhsKe5CRooNisBTh4SK119KrXXGmoK6V3kb8aH -f="<addrs>\n"
 `,
 	},
 	Arguments: []cmds.Argument{