Function addString
Merge branch 'master' of github.com:tdd-php/lib-simple-string into dev

Conflicts:
	SimpleString.php
	Tests/SimpleStringTest.php
Merge branch 'master' of github.com:tdd-php/lib-simple-string into dev

Conflicts:
	SimpleString.php
	Tests/SimpleStringTest.php
Merge branch 'master' of github.com:tdd-php/lib-simple-string into dev

Conflicts:
	SimpleString.php
	Tests/SimpleStringTest.php
Merge pull request #3 from wojtek25/dev

Function addString