viff could construct cases before running
refactoring `takeScreenshots` method
add inline diff.
replace `tookScreenshot` listener with `afterEach`
add `before` listener
add `after` listener
remove reporter from logic, only support `file` report now
update to generate image after each case.
remove report
update to 0.6.0
fix before listner is not triggered
use buffer directly rather than base64 encoded image.
use buffer directly rather than base64 encoded image.
Merge branch 'optimise_memory_usage' of github.com:winsonwq/viff into optimise_memory_usage
update Dependency of Mr.Async
Merge pull request #17 from winsonwq/optimise_memory_usage

Optimise memory usage