Comply with PSR-2 and Symfony convetions

Coding style is changed to comply with:
- [PSR-2 conding style](http://www.php-fig.org/psr/psr-2/)
- [Symfony Coding Standard](http://symfony.com/doc/current/contributing/code/standards.html)
- [Symfony Naming Convetions](http://symfony.com/doc/current/contributing/code/conventions.html)

Resolves #13.

Previous interface is left, but deprecated. Tests for deprecated methods
are also left so the old interface is kept valid unless explicitly
decided to be removed.
:lipstick: Reduce blank lines in tests
Put space after negation operator

Comply with PSR-2, but still leave space between the `!` operator and the expression afterwards.
Trigger E_USER_DEPRECATED errors for deprecated methods

This is the recommended way to deprecate functionality.
If you need to actually keep using the old interface, but still
upgrading to a new version you could disable deprecated errors from being
issues with:

    error_reporting(E_ALL & ~E_USER_DEPRECATED);

Unfortunately these are not easy to test with the latest PHPUnit version, so
I have suppressed these errors in the tests.
Merge pull request #16 from OpenBuildings/coding-style

Comply with PSR-2 and Symfony conventions