Document address types in preferential order

Author: carver

docs/conventions.rst

@@ -20,7 +20,7 @@ Addresses
 
 All addresses must be supplied in one of three ways:
 
-* A 20-byte binary address.
+* While connected to mainnet, an Ethereum Name Service name (often in the form ``myname.eth``)
 * A 20-byte hexadecimal that is checksummed using the `EIP-55
   <https://github.com/ethereum/EIPs/blob/master/EIPS/eip-55.md>`_ spec.
-* While connected to mainnet, an Ethereum Name Service name (often in the form ``myname.eth``)
+* A 20-byte binary address.