PSR-2 compliance

[tuupola]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Related tickets	mentioned in #24
License	MIT

What's in this PR?

Makes code PSR-2 compliant with the exception of relaxing the PSR1.Methods.CamelCapsMethodName for spec files. Additionally uses short array syntax in tests as discussed in #24. Lastly adds PHPCS to vendor and enables running it via $ composer phpcs.

I know this is three things in one PR but I feel these are closely related and the last one is easy remove if it is unwanted.

[sagikazarmark]

Thanks for the contribution, although I have a few problems with it:

• such changes should be discussed on the boilerplate repo first
• the spec files are kind of specially treated: they follow the PHPSpec style first, then PSR-1/2: so short array syntax, line breaking apply, camel case, method visibility for example do not.

[tuupola]

Ok. I though the camel case rule was the only one which should be relaxed.