add drone and update README

.drone.yml

@@ -0,0 +1,30 @@
+workspace:
+  base: /go
+  path: src/xorm.io/core
+
+clone:
+  git:
+    image: plugins/git:next
+    depth: 50
+    tags: true
+
+matrix:
+  GO_VERSION:
+    - 1.9
+    - 1.10
+    - 1.11
+    - 1.12
+
+pipeline:
+  test:
+    image: golang:${GO_VERSION}
+    environment:
+      GOPROXY: https://goproxy.cn
+    commands:
+      - go get -u golang.org/x/lint/golint
+      - go get -u github.com/stretchr/testify/assert
+      - go get -u github.com/go-xorm/sqlfiddle
+      - golint ./...
+      - go test -v -race -coverprofile=coverage.txt -covermode=atomic
+    when:
+      event: [ push, tag, pull_request ]

README.md

@@ -1,6 +1,6 @@
 Core is a lightweight wrapper of sql.DB.
 
-[![CircleCI](https://circleci.com/gh/go-xorm/core/tree/master.svg?style=svg)](https://circleci.com/gh/go-xorm/core/tree/master)
+[![Build Status](https://drone.gitea.com/api/badges/xorm/core/status.svg)](https://drone.gitea.com/xorm/core)
 
 # Open
 ```Go