Update sentry-raven to 0.15.6

Fixes a few bugs, most notably (for our purposes): https://github.com/getsentry/raven-ruby/pull/450

See merge request !2947

Adds "e" shortcut to issuable pages which redirects to the Edit page

Closes #13510

See merge request !2945

Show Crowd login even when sign-in is disabled

Fixes #13176.

See merge request !2749

Does not raise an error when Todo  is already marked as done

Closes #13681 

See merge request !2926

Set of UI fixes

* Improve wiki pages
* Improve profile pages

cc @skyruler 

See merge request !2758

Restrict permissions on public/uploads

Based on https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/631

See merge request !2764

Fixes issue with file view rows not clickable on project main view

Fixed an issue where it would only load the first 25 commit data on project main view.

Stopped the file view sending 1 too many requests.

Fixes #3916

See merge request !2933

fix some links



See merge request !2812

Users don't get instructions to push to other users empty projects

Fixes #12518

![Screen_Shot_2016-02-22_at_17.38.18](/uploads/42a3c32af1326f15a7b40fd7153a89fb/Screen_Shot_2016-02-22_at_17.38.18.png)

See merge request !2923

Issues can be dragged & dropped into empty milestone lists

This is also possible with MRs. Also fixed an issue where MRs weren't sortable

Fixes #13668

![milestone](/uploads/aada0f48ce8b1407cce920eef3f4d5f3/milestone.gif)

See merge request !2935

Fixed mis-aligned buttons on dashboard/issues

Before:

![](/uploads/35e413f2a5273bcdb1cc9ab20fa8d923/Screen_Shot_2016-02-22_at_10.15.39_PM.png)

After:

![Screen_Shot_2016-02-23_at_08.45.12](/uploads/4fbba0650ea6005b1cd600b5038f91d1/Screen_Shot_2016-02-23_at_08.45.12.png)


See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2921#note_3868715

See merge request !2932

Fixes dropdown appearance and makes it look accordingly to current design

Fixes #11874

See merge request !2920

This is also possible with MRs. Also fixed an issue where MRs weren't sortable

Fixes #13668

Extend specs for summary build status

Additional specs cover a case when one of the builds is running but
allowed to fail. Previous implementation returned `running` status,
which is wrong. This behavior has been changed in 8.5, this commit adds
missing specs.

See merge request !2904

Fix volatile spec.

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/312.

See merge request !206

Fixed an issue where it would only load the first 25 commit data on project main view
Stopped the file view sending 1 too many requests

Fixes #3916

Show project visibility level on project list

Fixes #3779

![Screen_Shot_2016-02-22_at_10.08.58](/uploads/611cc8aa2d12591d4fe6a70ba0f45d68/Screen_Shot_2016-02-22_at_10.08.58.png)

See merge request !2908

Added line links to blame table

Closes #4119

See merge request !2915

[ci skip]

Ensure we don't check a commit's description for revert message if it has no description

Fixes #13631.

/cc @razer6 @grzesiek @yorickpeterse @rdavila 

See merge request !2917

Properly set `auto_link_saml_user` default value in the Settings loader.

See merge request !2922

Fixed revert button tooltip placement causing movement

Before:

![moving-tooltip](/uploads/65cb9a41e8b8114fd8ee10d68cfd8206/moving-tooltip.gif)

After:

![moving-tooltip](/uploads/a1c36eb5735dc7592c49f6b5cb1469b5/moving-tooltip.gif)

See merge request !2910

Fixes #12518