Add project activity atom feed and show atom feed buttons everywhere where applicable.

See merge request !555

Change "Sam" to "Dmitriy" in feature steps

"Sam" was too short and generic and caused invalid test failures due to finding other people with names like "Sammie" or "Samuel" unexpectedly.

See https://ci.gitlab.com/projects/1/builds/35205 and https://ci.gitlab.com/projects/1/builds/35093 as two recent examples.

See merge request !571

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

"Sam" was too short and generic and caused invalid test failures due to
finding other people with names like "Sammie" or "Samuel" unexpectedly.

Update d3_rails and jquery-atwho-rails

We were a bit behind on these JS libs, so this updates them.

AtWho made a few API changes for which I had to update our usage.

Should fix #1457 as well.

See merge request !542

Update mentionable shared examples to be (a bit) more understandable

These shared examples were super confusing, and honestly still kind of are, but they should be a bit better now.

I encountered a bunch of headaches in these examples while refactoring ReferenceExtractor, so that's how I ended up changing it.

See merge request !1780

Add default_url_options initializer

Fixes #2266

See merge request !1791

Use fixed width icons in all nav sidebars

| Before (watch the Network and Graphs icons as the sidebar collapses): | After: |
| :--------: | :------: |
|![Screen_Recording_2015-04-23_at_02.31_PM.mov](https://gitlab.com/gitlab-org/gitlab-ce/uploads/338aa382ff7609978cd900db29379f3f/Screen_Recording_2015-04-23_at_02.31_PM.mov.gif)|![Screen_Recording_2015-04-23_at_02.30_PM.mov](https://gitlab.com/gitlab-org/gitlab-ce/uploads/24af635f253688690b42da60271e7afb/Screen_Recording_2015-04-23_at_02.30_PM.mov.gif)|

Uses the `icon` helper, because I can't help myself!

See merge request !566

Fixes #2266

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

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