fixed bug triggered by empty dirname in check_space
fixed bug where __file__ was used rather than cwd; found via acceptance tests
fixed unbound variable bug introduced by wacky indentation
updated ChangeLog
Merge branch 'master' of github.com:ged-lab/khmer into bug/empty_dirpath

Conflicts:
	ChangeLog
Merge pull request #360 from ged-lab/bug/empty_dirpath

fixed bug triggered by empty dirname in check_space