配置文件中增加captcha的下载。

godep.yaml

@@ -32,3 +32,5 @@ import:
     repo: https://git.qianqiusoft.com/github.com/xormplus__builder.git
   - package: github.com/xormplus/core
     repo: https://git.qianqiusoft.com/github.com/xormplus__core.git
+  - package: github.com/dchest/captcha
+    repo: https://github.com/dchest/captcha.git