rename config.h to config/os.h
rename config/os.h to config/os.hpp
correct mistake in Display.hpp's doc
add conversion routines
fix build system (add a tmp method run to GLFWDisplay)

Tigre is like Legos. The build system is on the User's side. The user
will build its own version of tigre based on its own, specific needs.
Tigre will provide examples and basic templates for Android, Linux
and Windows to make this task easier.
add Assert() and Exception class