mark/unmark bookmark - local information
update README.md
add pbhis command : show search history
update doc
add search in pbhis command
change history update threshold to 4 sec
Merge branch 'beta' of github.com:jmjeong/alfred-extension into beta

Conflicts:
	pinboard/history.py
	pinboard/info.plist
	pinboard/main.py
	pinboard/pinboard.alfredworkflow