Update help description for {min,max}GasPrice

Indicate expected values are in wei, and pose an example so it's clear given current gas prices. Closes #2032

cmd/livepeer/livepeer.go

@@ -117,8 +117,8 @@ func main() {
 	txTimeout := flag.Duration("transactionTimeout", 5*time.Minute, "Amount of time to wait for an Ethereum transaction to confirm before timing out")
 	maxTxReplacements := flag.Int("maxTransactionReplacements", 1, "Number of times to automatically replace pending Ethereum transactions")
 	gasLimit := flag.Int("gasLimit", 0, "Gas limit for ETH transactions")
-	minGasPrice := flag.Int64("minGasPrice", 0, "Minimum gas price for ETH transactions")
-	maxGasPrice := flag.Int("maxGasPrice", 0, "Maximum gas price for ETH transactions")
+	minGasPrice := flag.Int64("minGasPrice", 0, "Minimum gas price for ETH transactions in wei, 10 Gwei = 10000000000")
+	maxGasPrice := flag.Int("maxGasPrice", 0, "Maximum gas price for ETH transactions in wei, 40 Gwei = 40000000000")
 	ethController := flag.String("ethController", "", "Protocol smart contract address")
 	initializeRound := flag.Bool("initializeRound", false, "Set to true if running as a transcoder and the node should automatically initialize new rounds")
 	ticketEV := flag.String("ticketEV", "1000000000000", "The expected value for PM tickets")