non-working rectangle packer
tested & debugged on two cases (both heuristics); unknown if BF is *correct*.
fixed bugs related to the best-fit heuristic
rename 'stbrp_init_packer' to 'stbrp_init_target' since it must be called for every target;
clean up docs
doc tweaks
Merge branch 'working'
fix typo
duh, best-fit should tiebreak using waste, not prioritize waste (which makes bizarre towers)
Merge branch 'working'
Merge branch 'working' of https://github.com/nothings/stb
Merge branch 'master' of https://github.com/nothings/stb