[doc] English documentation

Author: nanmu42

README.md

@@ -5,6 +5,63 @@
 [![codecov](https://codecov.io/gh/nanmu42/etherscan-api/branch/master/graph/badge.svg)](https://codecov.io/gh/nanmu42/etherscan-api)
 [![GoDoc](https://godoc.org/github.com/nanmu42/etherscan-api?status.svg)](https://godoc.org/github.com/nanmu42/etherscan-api)
 
-Go bindings to the Etherscan.io API
+Go bindings to the Etherscan.io API, with nearly Full implementation(accounts, transactions, tokens, contracts, blocks, stats), full network support(Mainnet, Ropsten, Kovan, Rinkby, Tobalaba), and only depending on standard library. :wink:
 
-Under development now. :)
+![etherscan-api-go](https://user-images.githubusercontent.com/8143068/43701511-04762080-9989-11e8-8731-8504924da4e1.png)
+
+# Usage
+
+Create a API instance and off you go. :rocket:
+
+```go
+import (
+	"github.com/nanmu42/etherscan-api"
+	"fmt"
+)
+
+func main() {
+	// create a API client for specified ethereum net
+	// there are many pre-defined network in package
+	client := etherscan.New(etherscan.Mainnet, "[your API key]")
+
+	// (optional) add hooks, e.g. for rate limit
+	client.BeforeRequest = func(module, action string, param map[string]interface{}) error {
+		// ...
+	}
+	client.AfterRequest = func(module, action string, param map[string]interface{}, outcome interface{}, requestErr error) {
+		// ...
+	}
+
+	// check account balance
+	balance, err := client.AccountBalance("0x281055afc982d96fab65b3a49cac8b878184cb16")
+	if err != nil {
+		panic(err)
+	}
+	// balance in wei, in *big.Int type
+	fmt.Println(balance.Int())
+
+	// check token balance
+	tokenBalance, err := client.TokenBalance("contractAddress", "holderAddress")
+
+	// check ERC20 transactions from/to a specified address
+	transfers, err := client.ERC20Transfers("contractAddress", "address", startBlock, endBlock, page, offset)
+}
+```
+
+You may find full method list at [GoDoc](https://godoc.org/github.com/nanmu42/etherscan-api).
+
+# Etherscan API Key
+
+You may apply for an API key on [etherscan](https://etherscan.io/apis).
+
+> The Etherscan Ethereum Developer APIs are provided as a community service and without warranty, so please just use what you need and no more. They support both GET/POST requests and a rate limit of 5 requests/sec (exceed and you will be blocked). 
+
+# Paperwork Things
+
+I am not from Etherscan and I just find their service really useful, so I implement this. :smile:
+
+# License
+
+Use of this work is governed by a MIT License.
+
+You may find a license copy in project root.

doc.go

@@ -0,0 +1,9 @@
+// Package etherscan provides Go bindings to the Etherscan.io API.
+//
+// The implementation is with nearly Full implementation
+// (accounts, transactions, tokens, contracts, blocks, stats),
+// full network support(Mainnet, Ropsten, Kovan, Rinkby, Tobalaba),
+// and only depending on standard library.
+//
+// Example can be found at https://github.com/nanmu42/etherscan-api
+package etherscan