added windows shader
added color-halftone branch
added refs to new halftone
added windows shader
Merge branch 'windows' of github.com:tangram-map/tangram into windows

Conflicts:
	demos/gl_styles.yaml
	index.html
Merge branch 'master' into windows

Conflicts:
	demos/gl_styles.yaml
cleanup
removed unused uniforms
Merge pull request #9 from tangram-map/windows

Adding Windows shader
Merge branch 'master' into color-halftone

Conflicts:
	demos/gl_styles.yaml
	index.html
cleanup
cleanup
added color halftone
added gui controls and related tweaks
added animated flags and tweaked color-halftone settings
request redraw when uniforms are changed, and other cases where animation may not be active
Merge branch 'master' into color-halftone
extend mode-switcher in demo to correctly restore changes to mode & visibility on all layers
demo: only modes that need to be redrawn independent of viewport movement need to be marked as 'animated'
demos: small mode re-arrangement