chore(mixins): add .font() for creating @font-face

Also move the icon font to the new mixin and adapt necessary
variables.
fix(icons): use better alignment relative to text
fix(tooltip): don't show if element no longer in DOM

If the element is removed from the dom before the tooltip delay,
the tooltip would show, what is not the right case.
fix(tooltip): hide on element destroyed

Whenever a $destroy event is triggered in an element with an active
tooltip, the tooltip will no longer remain viisble.

Fixes #64
chore(release): release 0.3.2
Merge branch 'master' into gh-pages
chore(release): docs release v0.3.2