edits in search.py (#384)
edits in search.py (#384)

* added documentation, standardised docstring quotes

* made search.py pep8 compatible using flake8

* fixed bug in OnlineDFSAgent

SnShine/aima-python,sofmonk/aima-python,jo-tez/aima-python,jo-tez/aima-python,sofmonk/aima-python,Chipe1/aima-python,aimacode/aima-python,aimacode/aima-python,SnShine/aima-python,Chipe1/aima-python