Warning: Ending support for PHP 5.3 and 5.4

[bishopb]

PHP 5.3 reached end of life on 2014-08-14. PHP 5.4 reached end of life on 2015-09-03. By Internet time standards, that's ancient history.

Consistent with our proposed Long-Term Support policy, we'll be dropping support for PHP 5.3 and 5.4 in the next release of v1.x series.