update gitlab shell to 1.9.8 for gitlab 7.2.2

As committed in https://github.com/gitlabhq/gitlabhq/commit/873acfd9aa54e801d5786c32b05c4f8ad21af72a GitLab 7.2.2 requires GitLab Shell 1.9.8. Related to https://github.com/gitlabhq/gitlabhq/pull/7806 & https://github.com/gitlabhq/gitlabhq/pull/7809.

Check for hooks directory symlink in gitlab:check

See merge request !1098

Conflicts:
	lib/tasks/gitlab/check.rake

This reverts commit d38df040.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Hooks migration skipper

See merge request !1093

Stable xss fix

See merge request !1048

RAW feature
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Protect unsubscribe path

See merge request !1033

Backticks cause quote

See merge request !704

Swap is required on servers with 1GB RAM

See merge request !1032

Bump required gitlab-shell version to 1.9.7

See merge request !1031

Add installing cmake to 7.2 update docs

See merge request !1029

Add dependency info for mysql-postgresql converter

upgrade ruby and gitlab shell config during 6.0->7.1 & 6.0->7.2 upgrades

Explain label migration

See merge request !1025

Update changelog

Fixes #1509

See merge request !1026

cmake is required during the installation of the rugged gem

Running converter with Python 2.6.x installed gives the following error:
AttributeError: 'module' object has no attribute 'check_output'

After installing Python 2.7.x everything works fine.

Fix spelling error in merge request performance issue warning.