experimenting with YAML for the style file (for the multi-line string support, for shader snippets)
- add support for style 'macros' (white-listed style computing functions) in YAML styles
- make YAML style support co-exist w/JSON support
- make YAML support optional by moving to separate browserified file (parser is large, not sure we want it in core lib)
- generalize support for code that only needs to run in the main thread (not in workers)
add extracted YAML parser to makefile dependencies
continue to fix/refine YAML stylesheet
add support for stylesheet shader snippets to be inline block of GLSL, or a URL to retrieve GLSL block from
Merge branch 'modes' into yaml

Conflicts:
	dist/vector-map-worker.min.js
	dist/vector-map.debug.js
	dist/vector-map.min.js
move screen spotlight effect to shader snippet