fix old reference to $element

data-uk-button triggered error when clicked due to old reference to $element
Fixes #577
Fixes #449
updated docs  - typo
Merge branch 'master' of github.com:uikit/uikit
addons cover doc updated
added cover test
updated version and dists
updated docs - cover add-on
Merge branch 'master' of github.com:uikit/uikit

Conflicts:
	docs/addons_cover.html
dom observe docs updated
updated docs - cover add-on
Merge branch 'master' of github.com:uikit/uikit
Update README.md
tab.js cleanup
Merge pull request #565 from malles/patch-1

fix old reference to $element
removed unused stickyId variable
Added additional input types for iOS style reset to form component
Sortable.js breaks browser tab shortcuts

Shortcuts like click+cmd, click+ctrl in browsers that allow opening links in the background is broken.
ctrlKey and metaKey (metaKey is the cmd key on the mac) usually open links in new tabs in the background, Chrome does it like this.
shiftKey in Chrome opens a link in a new window.
Merge pull request #600 from stipsan/patch-1

Sortable.js breaks browser tab shortcuts