add readme

README.md

@@ -0,0 +1,74 @@
+[中文](https://github.com/go-xorm/xorm/blob/master/README_CN.md)
+
+Core is a light wrapper of sql.DB.
+
+# Open
+```Go
+db, _ := core.Open(db, connstr)
+```
+
+# SetMapper
+```Go
+db.SetMapper(SameMapper())
+```
+
+# More scan usage
+```Go
+
+rows, _ := db.Query()
+for rows.Next() {
+    rows.Scan()
+    rows.ScanMap()
+    rows.ScanSlice()
+    rows.ScanStructByName()
+    rows.ScanStructByIndex()
+}
+```
+
+# More Query usage
+```Go
+rows, err := db.Query("select * from table where name = ?", name)
+
+rows, err := db.QueryStruct("select * from table where name = ?Name",
+            &user)
+
+var user = map[string]interface{}{
+    "name": "lunny",
+}
+rows, err = db.QueryMap("select * from table where name = ?name",
+            &user)
+```
+
+# More QueryRow usage
+```Go
+rows, err := db.QueryRow("select * from table where name = ?", name)
+
+rows, err := db.QueryRowStruct("select * from table where name = ?Name",
+            &user)
+var user = map[string]interface{}{
+    "name": "lunny",
+}
+rows, err = db.QueryRowMap("select * from table where name = ?name",
+            &user)
+```
+
+# More Exec usage
+```Go
+db.Exec("insert into user (`name`, title, age, alias, nick_name,created) values (?,?,?,?,?,?)", name, title, age, alias...)
+
+user = User{
+    Name:"lunny",
+    Title:"test",
+    Age: 18,
+}
+result, err = db.ExecStruct("insert into user (`name`, title, age, alias, nick_name,created) values (?Name,?Title,?Age,?Alias,?NickName,?Created)",
+            &user)
+
+var user = map[string]interface{}{
+    "Name": "lunny",
+    "Title": "test",
+    "Age": 18,
+}
+result, err = db.ExecMap("insert into user (`name`, title, age, alias, nick_name,created) values (?Name,?Title,?Age,?Alias,?NickName,?Created)",
+            &user)
+```