!!Creole 0.2 spec proposed

Changes from [Creole 0.1]:
* Images now {{{ <<flower.png>> }}} (was {{{ {{flower.png}} }}}) - to make it easier to type
* Pre now {{{ {{ pre }} }}} (was {{{ {{{ ~}}} }}}) - to conform with other syntax being two characters
* Placeholder now {{{ [{x}] }}} (was <<x>>) - remove collision with images