added method to destroy all textures for a given GL context
added a method to destroy a GL program wrapper and free associated resources
leave in a debug line, remove a stray line
add methods to destroy a single mode instances, or all modes for a given GL context
avoid race conditions that can lead to multiple copies of render mode GL programs
more thorough clean-up on scene destroy
expose layer in demo for debugging
update build
lint
mark scene when destroyed to prevent errors on further calls
leaflet layer: unhook leaflet events and destroy tangram scene when layer is removed
pull geometry forward in depth range to avoid far clipping plane
keep base layer from disappearing when post-processing depth values
put polygon and line outlines between layers to present z-fighting
(note: this needs more nuanced consideration when defining more styling/placement rules)
remove old style file
WIP leaflet tests (layer add works but known issues w/layer removal)
add stylesheet option to draw tile edges on polygon outlines (mostly for debugging)
Increase the default timeout for tile requests
Merge pull request #42 from tangrams/update-timeout

Increase the default timeout for tile requests
WIP callback for Scene.rebuildTiles()
(known issues when encountering tile errors such as network problems)