Changes

v1.1.1 - 3/14/17

(Fix) rebase appropriately

v1.1.0 - 3/14/17

Allow sources to fail, effecting fallback (@jingsam)

v1.0.3 - 12/28/15

Don't composite empty buffers

v1.0.2 - 10/22/15

Use async image encoding when concatenating rasters
Load sources on each request

v1.0.1 - 9/26/15

Use actual, not original coordinates when concatenating vector tiles

v1.0.0 - 11/24/14

Initial version