Log Message:
Update ruby-mechanize to 2.7.5.

=== 2.7.5

* New Features
  * All 4xx responses and RedirectLimitReachedError when fetching robots.txt are \ 
treated as full allow just like Googlebot does.
  * Enable support for mime-types > 3.

* Bug fix
  * Don't cause infinite loop when `GET /robots.txt` redirects. (#457)
  * Fix basic authentication for a realm that contains uppercase characters. \ 
(#458, #459)
  * Fix encoding error when uploading a file which name is non-ASCII. (#333)