Version 4.0.0.

Summarized list of changes for 4.0.0:
	- Added support to prevent catastrophic failure
	  when dynamic memory allocation fails.
	- Error code assignment now guaranteed when using
	  flub_toss().
	- Fixed realloc() bug in flub_append().
	- Refactored stack trace representation/printing.
	- Fixed compiler errors when debugging.
	- Updated README.