Calculate arrow offset without border

[Spenhouet]

Fixing issue: #325

Minimal example: http://fiddle.jshell.net/x62303x6/

Changes the arrow offset calculation to be calculated without border since the arrow is moved relative to the content bubble.

el.offsetWidth & el.offsetHeight => width + padding + border el.clientWidth & el.clientHeight => height + padding

Therefor use clientWidth & clientHeight for the arrow offset instead of offsetWidth & offsetHeight.

[Spenhouet]

@zimmi88 I don't know why the tests failed. I tried to merge the changes from the master into this pull request. Not sure if something went wrong there. My changes are very small. Maybe you could take a look at it and merge this pull request.

[timlindvall]

Doesn't look like this failure is due to the change. Nonetheless, I'd like to figure out why the build is failing. Time permitting, I'll dig into this.