Initial commit of walk() and find() methods on the stix.Entity class
Merge remote-tracking branch 'origin/master' into walk
Fixed issue where ObjectProperties._parent caused duplication of yielded walk objects
Fixed bug in descend(). Changed yieldable tuple to be just stix and cybox Entity classes
Update ex_walk.py
Merge remote-tracking branch 'origin/master' into walk
Small cleanup
Merge pull request #155 from STIXProject/walk

Added walk() and find() methods