* change the error info for captcha field.
Merge branch 'master' of git@github.com:xirang/xirangeps
 * return the captcha form directly.
Merge branch 'master' of git@github.com:xirang/xirangeps
 + import the captcha module.
 * use captcha module instead.
 * move the logic of captcha to captcha module.
Merge branch 'master' of git@github.com:xirang/xirangeps
 * adjust code format.
 * adjust code format.