Fix shell commands in shell install

Fixes #1610

See merge request !1320

Dropdown icon not clickable

Fixes #1642 by using `pointer-events` property supported by [modern browsers](http://caniuse.com/#search=pointer-events)

See merge request !1319

Show files named diff

Fixes #1749

See merge request !1318

Add an extra reference to the 'shell commands' guide

The 'shell commands' guide now also has tips on opening/reading files and handling paths.

See merge request !1321

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

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Add security tips about file and paths

These are some extra guidelines to guard against code execution and path traversal.

See merge request !1317

Updated doc/integration/twitter.md, fixed incorrect callback URL

Fixed a typo in the Integration instructions for Twitter OAuth

See merge request !257

(referencing /users/auth/github/callback,
 not /users/auth/twitter/callback)

Speed up omniauth AddIdentityTable migration

https://dev.gitlab.org/gitlab/gitlabhq/issues/1810

See merge request !1315

Unicorn workers

See merge request !1316

Unicorn advice

See merge request !1314

Add 'grace time' behavior to Sidekiq MemoryKiller

The previous iteration of the memory killer did not give 'large'
jobs much of a chance to finish. This caused them to come back after
each restart, leading to another memory-induced shutdown. By adding
some 'grace time' between the moment we detect a memory peak and
the moment we start shutting down, we hope to give Sidekiq a chance
to get whatever causes its memory to grow 'out of its system'.

See merge request !1313

Drop vagrant from issue tracker guidelines

Is this the preferred method of reproducing an issue? If yes, disregard this MR.

\cc @sytses @marin

See merge request !255

Move sidekiq debug docs to development folder

Conflicts:
	spec/routing/project_routing_spec.rb

Attachment url should not be overwritten

Fixes #1786

See merge request !1308

Improve Monokai highlight style to match original

The current monokai style is not very true to the original and lacks colors for certain syntactic items as mentioned in ticket https://github.com/gitlabhq/gitlabhq/issues/6855. This change's goal is to bring the monokai highlight style in line with the original design from http://www.monokai.nl/blog/2006/07/15/textmate-color-theme/

Before:
![monokai-old](https://gitlab.com/uploads/klowner/gitlab-ce/ce96c7d7c2/monokai-old.png)

After:
![monokai](https://gitlab.com/uploads/klowner/gitlab-ce/b257a8143a/monokai.png)

See merge request !238

Improve activity UI

See merge request !1311

Small fixes

Improve application stability over unexpected cases

See merge request !1310