Merge pull request #1 from netvl/master

Proper cargo support, with examples
glfw-rs and gl-rs only needed for demo
demo broken, because underlying static lib not found: try extern link kind='static'
nbd: typo and unneeded 'mut'
update readme
porting blendish, as a nice UI example that uses nanovg
merge a couple of netvl's changes; start a wrapper for transforms
working the blendish example, not done yet
fix text_bounds
fixes to demo: handle text bounds correctly; and update for Color
added 'text_advance', when you don't need full text bounds
first time success compile of blendish demo -- not near running yet tho
wiring up the blendish demo, no works yet
moved non-working examples to separate project
tweak build, add blendish mention to readme
merging netvl's image handle
unfarking the readme
image creation now returns Option<Image>, to avoid confusion over failure values (img fails with 0, fnt fails with -1)
handles (and Option<Font> returns) for Font creation fns
use ffi constants for image- and font- creation-failure flags