Making the codebase PSR2

Depends on https://github.com/Bit-Wasp/bitcoin-lib-php/pull/26



excluded the following 2 validations for now:
 - PSR1.Methods.CamelCapsMethodName.NotCamelCaps
 - PSR2.Methods.MethodDeclaration.Underscore

Because to 'fix' those 2 we have to make a lot of changes to the API which would would backwards compatability completely ...