Subscription to issue/mr

Fixes #1911 and #1909

![joxi_screenshot_1426601822159](https://dev.gitlab.org/gitlab/gitlabhq/uploads/53021bc5783271322ab2dfba7598eaa3/joxi_screenshot_1426601822159.png)

![joxi_screenshot_1426601836423](https://dev.gitlab.org/gitlab/gitlabhq/uploads/244ff360fbd6f30980f8dad699400814/joxi_screenshot_1426601836423.png)

See merge request !1702

It is same search like we have at issues page. It allows to quickly
filter merge requests based on title or desription. I copy-pasted some
js code from Issues.js. In future search (filtering) logic should be
refactoed into one class for merge requests and issues

Fix server error when editing a note to "+1" or "-1"

### Summary

If a user edits a comment with "+1" or "-1" in the beginning, the POST returns an Internal Server error. (issue #1151). This merge request resolves that error.

### Steps to reproduce

1. Comment on an issue with "Test comment".
2. Edit the issue.
3. Write "+1" and click "Save Comment".

### Expected behavior

The edited note should be saved and refreshed. Any previous upvotes/downvotes from the user should contain a strikethrough.

### Observed behavior

Internal Error

### Relevant logs

```
Started PUT "/avocode/avocode-manager/notes/4996" for 185.33.136.107 at 2015-02-28 17:11:53 +0100
Processing by Projects::NotesController#update as JS
Parameters: {"utf8"=>"✓", "authenticity_token"=>"*removed*", "note"=>{"note"=>"+1\r\n\r\nYes"}, "commit"=>"Save Comment", "project_id"=>"avocode/avocode-manager", "id"=>"4996"}
Completed 500 Internal Server Error in 86ms
ActionView::Template::Error (undefined method `each' for nil:NilClass):
28: %span.note-last-update
29: = note_timestamp(note)
30:
31: - if note.superceded?(@notes)
32: - if note.upvote?
33: %span.vote.upvote.label.label-gray.strikethrough
34: %i.fa.fa-thumbs-up
app/models/note.rb:495:in `superceded?'
app/views/projects/notes/_note.html.haml:31:in `_app_views_projects_notes__note_html_haml___812277000516355462_69988235638820'
app/controllers/projects/notes_controller.rb:71:in `note_to_html'
app/controllers/projects/notes_controller.rb:103:in `render_note_json'
app/controllers/projects/notes_controller.rb:39:in `block (2 levels) in update'
app/controllers/projects/notes_controller.rb:38:in `update'
```

### Fix

It turns out no tests were present for the "Edit Issue" functionality. I added spinach tests to exercise this and reproduced the error.

Most of the routes in `notes_controller.rb` appear to render all notes for the given discussion. `_form.html.haml` needs the full list of notes commented by the user to add strikethroughs for older upvotes/downvotes. However, only the `index` route appeared to obtain this information. The fix is to add a `before_filter` to obtain all the user's notes beforehand, except in the delete case where this information is not needed.

Things to watch: `NotesFinder` needs `target_type` and `target_id` to determine what to do. I'm not sure if there is a conscious effort to phase these keywords out in favor of `noteable_type` and `noteable_id`.

See merge request !360

Closes #1151

Irker is a gateway which sends IRC messages on git updates. This new
service provides an interface to this gateway, integrated in Gitlab, for
each updates.
As per the guidelines, this commit adds the new feature in the
CHANGELOG, tests and documentation.

See http://www.catb.org/esr/irker/