add documentation

Documentation/ERC20.md

@@ -0,0 +1,47 @@
+# ERC20 Token
+
+## Transfer
+
+* Create an instance of an ERC20 token
+
+```swift
+let erc20Token = ERC20(contractAddress: "0xd26114cd6EE289AccF82350c8d8487fedB8A0C07", decimal: 18, symbol: "OMG")
+```
+
+* Create a data parameter which will be sent with `RawTransaction` data section
+
+**Put contract address to `RawTransaction` `to` parameter**
+
+```swift
+let parameterData: Data
+do {
+    parameterData = try erc20Token.generateDataParameter(toAddress: "0x88b44BC83add758A3642130619D61682282850Df", amount: "100")
+} catch let error {
+    fatalError("Error: \(error.localizedDescription)")
+}
+
+let rawTransaction = RawTransaction(
+    wei: "0",
+    to: erc20Token.contractAddress,
+    gasPrice: Converter.toWei(GWei: 10),
+    gasLimit: 21000,
+    nonce: 10,
+    data: parameterData
+)
+```
+
+* Sign tx and send a parameter data with `sendRawTransaction` RPC
+
+```swift        
+
+let tx: String
+do {
+    tx = try wallet.sign(rawTransaction: rawTransaction)
+} catch let error {
+    fatalError("Error: \(error.localizedDescription)")
+}
+
+geth.sendRawTransaction(rawTransaction: tx) { result in
+    // do something with response
+}
+```

README.md

@@ -42,6 +42,7 @@ geth.sendRawTransaction(rawTransaction: tx) { result in
 ## Documentations
 
 - [Getting Started](Documentation/GettingStarted.md)
+- [ERC20 Token](Documentation/ERC20.md)
 - [JSONRPC API](Documentation/JSONRPC.md)
 - [Etherscan API](Documentation/Etherscan.md)