By eager-loading the Mail gem in the Sidekiq initializer.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Updated Sidekiq to 3.5.x

When enabled, this middleware allows Sidekiq to detect that its RSS has
exceeded a maximum value, triggering a graceful shutdown. This
middleware should be combined with external process supervision that
will restart Sidekiq after the graceful shutdown, such as Runit.

Allow connection to Redis via unix socket, using
unix:/var/run/redis/redis.sock for example.

Default behaviour does not change, except that the full Redis URL must
be configured, with redis:// for tcp or unix: for unix socket.

* .page_title  class added. Used for better page headers
* improved help page
* added back links for help pages
* show app version & revision on help page

Backend changes:
* Gitab::Version && Gitlab::Revision constants