21 batched rendering

[mrozbarry]

Tasks

• [x] Create context wrapper that behaves like context2d
• [x] Add zTweaking
• [x] Add better transparency HoF
• [x] Change operations to something serialize-able so it can be more easily tested. Probably [operationName, ...arguments]

Tickets

• Closes #21

[johnblackspear]

Looks great man!

I have one question - I've been thinking that some items could have an arbitrary z-index. For example, we can set a decoration to either be above (parentZIndex -1) or below (parentZIndex + 1) the parent block, as some decorations look better in front (e.g. shrub) or behind (stone) the parent.

I'm not sure how we'd do this using the current drawImage (maybe add another addOperation call, like drawImageAtZIndex, or an optional passed to drawImage) - but as it's such a minor enhancement it can obviously wait :)

Merge it :D

[mrozbarry]

@johnblackspear Might be space for context.atZ(ArbitraryZValueHere, (tweak) => {}), but we'll worry about implementing that when we need it.