tidy Makefile to be consistent with conventions

[dmalan]

I reorganized the repo to essentially put everything in c/ and java/ subdirectories, with a top-level Makefilethat builds everything into build/. That way, all a user needs to do is install whatever is inbuild/and can ignore everything else. It remains a to-do to auto-generatebuild/docs`, so for now its in the top-level too.

Would be ideal not to hard-code so much in the Makefile, though?

https://github.com/cs50/spl/blob/master/Makefile

• tidy Makefile
• determine when best to remove build/obj/ (so that once make is done, everything is staged in build/, for make install); right now, make install depends on libcs.a, which is thus depending on obj/ not yet being deleted

[dmalan]

Actually, @kzidane, want to ready this for deployment via launchpad, such that its usage becomes

#include <cs50/spl.h>

?

[kzidane]

Sure, once all is good with cs50/libcs50!