Set tooltip arrow size with variable

The size of the tooltip arrow can now be set with a variable. This
commit does not reposition the tooltip yet. So if you set
$effeckt-tooltip-arrow-size to 15px or something it will overlap the
text.
Added npm-debug.log to .gitignore
Merge pull request #299 from MichielBijl/master

Added some variable magic to tooltips.scss