Bump libv8

This fixes development issues on OS X 10.10. Version 3.16.14.3 is hard
to install for some reason for some people (me).

See merge request !101

Make the schedule_build cron job quiet

As an administrator, it is not interesting for me to get emails from
GitLab CI that look like:

```
.
.
.
.
```

See merge request !100

This fixes development issues on OS X 10.10. Version 3.16.14.3 is hard
to install for some reason for some people (me).

As an administrator, it is not interesting for me to get emails from
GitLab CI that look like:

```
.
.
.
.
```

Update platform requirements

Last_build fix

See merge request !99

Changed sudo by su -c

API for webhooks registering

Simple API method for creating new WebHooks for specified Project.

P.S. Sorry for not squasing commits, they were already pushed.

See merge request !11

Add Branch and Message to Emails

Added git branch and commit message to all the email templates. This makes it easier to know how to deal with the email when you can't (or don't want to) click on the link.

See merge request !17

Add pending.png and canceled.png images for build status

Fixes https://gitlab.com/gitlab-org/gitlab-ci/issues/53

See merge request !20

Register specific runner via API without admin access

See merge request !21

You can provide project token durinng runner regstration and runner will
be created specifically for this project

Example dev unicorn

**What does this PR do?**

It adds an unicorn file for development purposes

**Why is this PR needed?**

It helps the development of the Development Toolkit for CI

See merge request !16

Corrected API documentation link

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

5.3 update guide

Added update guide from 5.2 to 5.3

See merge request !98

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

Update Changelog for 5.3 release

Updated changelog

See merge request !96