Url::unescape() optimized for performance
ObjectMixin: nearly not measurable optimizations
Html: floats in attributes are printed in natural notation [Closes nette/forms#50]
Strings::substring(): unified behavior when both start and length are negative

behavior of iconv_substr is inconsistent with mb_substr (http://3v4l.org/JvOlj)
Strings::toAscii(): unsupported characters are removed instead of being replaced with '?'
Strings::length uses mb_string if available
Strings::substring(): avoid calculating string length unless necessary
Json: workaroud for PHP fatal error caused by \u0000 at the beginning of key
improved phpDoc