Set default timezone to UTC in tests/bootstrap.php

In order to don’t get that infamous error message:
“[…]It is not safe to rely on the system's timezone settings[…]”

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Move phpunit.xml.dist to root of project

Now, it’s possible to run just `phpunit` in root of project, instead of
`phpunit XXXXXXX XXXXX XXXX XXXXX`, because
XML configuration file holds all the flags needed (including
coverage-text).

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Self-update composer instead of re-download and remove --dev flag

`composer` is already available in all Travis-CI installations, so, it’s
just a matter of self-update it in order to having the latest version.

The `--dev` flag in `composer install` is enabled by default, so it’s
not necessary.

Last, `composer` is installed globally in Travis-CI envs, so it not
needed to prepend `php` to commands.

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Make travis run `phpunit` taking advantage of phpunit.xml.dist

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Make Travis PHP tests execute also in hhvm (with allowed failures) and 5.5

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Merge pull request #3 from rogeriopradoj/phpunit-plus

PHPUnit plus