RPC return value for 0

[ethers]

The return value for 0 should be 0x

In addition to the 2 cases below, please review and fix any other APIs. (The 2 cases below are eth_getBalance and eth_getTransactionCount returning 0x0 and 0 respectively. Note, with eth_getTransactionCount the spec says the return value should be hex string https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_gettransactioncount )

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_getBalance","params":["0xfd4ed114ef85d350d6d40ed3f6dc23743f8f99c4", "latest"],"id":1}' http://localhost:8080
{
    "id": 1,
    "jsonrpc": "2.0",
    "result": "0x0"
}%                                  

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_getTransactionCount","params":["0x9dc2299a76b68b7ffa9e3ba0fd8cd7646d21d400","pending"],"id":1}' http://localhost:8080
{
    "id": 1,
    "jsonrpc": "2.0",
    "result": 0
}%

[ethers]

Update per ethereum/aleth#1433 is 0 should be 0x0

[tgerring]

Fix merged in 779a51c