Enable inline PHP syntax highlighting

Pygments has a "startinline" option which is only relevant for the PhpLexer. It allows syntax highlighting without the opening <?php tag. I believe this option is ignored for every other lexer.

Could you either set this to true by default using the proposed change? Or could this be exposed as a setting somewhere in _config.yml? I can't think of a reason someone would not want this enabled.
Merge pull request #1141 from joelclermont/patch-1

Enable inline PHP syntax highlighting