Resolve "Skip security review when only update docs"

To skip security review in certain conditions, I modified the applicable function of the SecurityReviewBase. I added a function not_every_change_is_jh_doc_change? to it, and this function will call the api of Jihulab to get the all changes of the appointed MR. Then this function will check if all the changes' path is behind jh/doc.

Closes #25 (closed)