Support match case syntax

[yota-code]

Hi,

I'm missing the handling of match / case control flow.
With mako 1.3.10 I get the following error when I try to use %match expr : somewhere in my template

mako.exceptions.CompileException: Unsupported control keyword: 'match'

I looked up the current open issues and couldn't find something close, so I made a new one

[cocolato]

Mako doesn't support the newer Python syntax now, so you should use an if/else instead.