Implemented prototype Light & Heavy batches in a separate module.
Implemented draw_batch
Implemented Batch trait for both light and heavy variants.
Ported the examples to use batches
Added docs, cleaned up the code
Cleaned up old Program trait. Improved comments.
Implemented Graphics class, added HeavyBatch typedef to shader_param, moved examples to the Graphics
Renamed batches to RefBatch and OwnedBatch
Merge pull request #285 from sectopod/batch

Batching
Added comments to our device attributes
Implemented instance_rate property of vertex attributes
Implemented instance rate divisor on the device
Implemented instanced calls on the device
Implemented front-end support for instancing
Minor formatting fixes to attribute types and vertex format macro
Merge pull request #289 from sectopod/instance

Instancing
Use mask_write

Closes #148
Remove undefined behavior in offset computation

Closes #156
Merge pull request #291 from cmr/mask_write

Use mask_write
Merge pull request #292 from cmr/offset_of

Remove undefined behavior in offset computation