Save png with selenium driver.

Simple test code to save webpage's view
to png file.
Merge remote-tracking branch 'origin/master'
Get b64 buffer of screenshot ans save it to png.

Backend pass image data to frontend not using file but buffer.
So write test of it.
Move selenium test file to test folder.
Make html file which have image of given url.
Return base64 format of png image.
Merge remote-tracking branch 'origin/master'
Merge pull request #1 from majecty/master

Get url return base 64 of png.