Bump gitlab shell

Add markdown styleguide.

Add ability to set different ssh host, if different from http/https

Complete admin APIs for SSH Keys

added target_project_id to merge_requests.md

Include SASS in subdirectories with glob.

Break up the long upgrade one liner & add Bash syntax highlighting

Give the Rails cache its own Redis namespace

Missing part of active user

Added description about optional field target_project_id for merge requests.

Version680

VERSION to 6.8.0

Update Shell version in the Install doc

Allow to overwrite location of gitlab.yml config file.

Allow to specify secret token via SECRET_KEY_BASE environment variable.

Detailed monthly release

Fixes #1190

Fix minor typo in docs

512mb

Most people only care about the 512mb option, we should mention that with one worked you don't get http pushes.

Update title and revert section of 6.7-to-6.8 docs

fix installation.md typo

Complements POST operation added in gitlabhq/gitlabhq#3146

Implement DELETE /users/:uid/keys/:id for admin users

Fix "Line is too long. [83/80]"

Use single quotes as advised

Use single quotes as advised

Use single quotes as advised

Fix missing space around { and }

Fix typo in documentation

Only catch  ActiveRecord::RecordNotFound, let other exceptions propagate

Raise a "404 Not found" if key to be deleted cannot be found
As requested by @jvanbaarsen in https://github.com/gitlabhq/gitlabhq/pull/6781#discussion_r11735114

Remove tab
Unconfigured vim on this box, grrrr./

depency -> dependency

Workflow documentation

Help pages on doc.gitlab.com/ce are missing titles. This needs to be
solved globally.

This text was deleted in 564c37d9.

Update monthly release doc

/cc @sytse @jacobvosmaer @marin