Move to PHP5.4 and remove from/import.
Wrong append and prepend algorithm.

Internally, the direction does not matter. It does not require to
consider the direction to append or prepend.
Fix `compare` if `Collator` is not present.
Fix flags between global and local in `match`.
Add tests.
New `toCode` method, without UCS-2.

UCS does not support characters above U+FFFF so we use a custom `toCode`
method.
Tests are green now.
Use hexadecimal everywhere.
`toBinaryCode` has a better semantics.
Add tests for Hoa\String\Search.
Review.

Thanks @jubianchi!