remove tests numbering; more tests
gruntfile refactor
tests/index.js refactor
update png-diff (won't sync throw anymore)
move 'all tasks skipped' from passing warning test to fail test
`mouseup` is the accurate event to listen to while recording clicks
new bad screenshot size test case
bad ss got in; remove
major refactor with features addition

Check HISTORY.md v0.6.0
update readme and bump package.json version