Introduction to PSR-2 Codestyle

## What
A change to introduce [PSR-2 codestyle](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md).
I've used 2 separate commits on purpose to group the general indentation changes apart from a [small refactoring](https://github.com/david4worx/forceutf8/commit/c41fcdee73e468df73029dc1898f5df5f3d84cc4).

## Why
* Consistent to read code
* Gives better overview
* Helps tools like PHP_CodeSniffer

## Whats changed
* All tabs have been replaced by 4 spaces
* Control structures are now PSR-2 compliant
* Every class method and variable have a declared visibility
* Refactored the if statements for checking/guessing multi-byte strings into separate variables that are re-used
* No line is longer then the hard limit of 80 chars.

## What will come?
* A decrease in cyclomatic complexity (removing not needed else(if) statement and utilizing fast returns)
* Docblox
* A (possible?) fix for an [EURO sign problem](http://nl3.php.net/manual/en/function.utf8-decode.php#88488)