Add a Linux/Unix Makefile

This commit adds a Makefile enabling easy compiling using Linux
or other unix like operating systems.

'size_t' was not defined here (using Ubuntu 13.10), I needed to
include some headers.

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Merge pull request #6 from stefanbeller/compilable

Add a Linux/Unix Makefile