Fix immediate seg fault, check for argc before checking help
Address issue #9 by moving code from sig handler to main loop.

It appears calling endwin() and refresh() in the signal handler
handle_winch were casuing seg faults, so they were moved.

Display of the resize information was also problematic and thus
removed.
init/resize values accept int instead of size_t to handle negative graph size
Address issue #9, add checks for negative values on draw functions
Update screenshot and description in README
Changed from std=c99 to std=gnu99 since strsep is not standard