Altering directory structure

The sources are only for chesspp, so it makes no sense to have another
directory.
Also `main' is together with the other sources
makefile

extracted from http://users.softlab.ece.ntua.gr/~ttsiod/makefile.html
Handles dependencies, debug and release
Fixed includes

Not using relatives.
Let the makefile to take care
Handling dependecies
Included libraries

json linked statically
Fixed dependencies issues
Generating dependencies
Usage example
Merge pull request #29 from ne555/master

Makefile that works. Thank you ne555. 
Note: The order in which SFML libraries are linked matters.