Replace iterator with plain pointer and add tests

Updated implementation (#8)

* replace iterator with plain pointer and add tests

* bump to php 7.4

* add github actions

* update phpunit config

* allow new ascii-table package

* remove phpdox from readme

Add support PHP 7.4

Merge pull request #7 from IlyaSerdyuk/master

Add support PHP 7.4

v1.1.0: Merge pull request #5 from dmryabov/remove-hoa-ustring

remove hoa/ustring dependency

v1.0.2

Remove check on empty string

v1.0.1

Merge pull request #2 from LTD-Beget/unicode

unicode

v1.0.0

String stream data structure