Adding ability to handle 'opened' item property

Adding ability to handle opened property on items with children. When configured as true, the subgroup dropdown for children will automatically be open if the item is overflowed or the navigation is in collapsed or vertical state.

Replacing `vertical-expanded` property with `vertical-opened-at`

Added new property vertical-opened-at which allows for dynamic open and close behaviour on vertical navigations. vertical-expanded is no longer necessary as the vertical navigation can be configured to be opened permanently be setting vertical-expanded-at to 0.

Adding title attribute to item and subitem labels

Adding title attribute to items and subitems labels, in order to enable tooltips on hover.

Fixing collapsed and vertical state width, padding and box-shadow

Design compliance with respect to padding and width of items and subitems, as well as adjustments for box shadows in collapsed mode.

v2.3.0

• Items now support href and window properties for navigation to user-defined URLs
• Added delaySlideAnimation property to px-app-nav for optionally specifying a timeout (in ms) before the vertical nav expands after hover

Thanks @leebickmtu for these additions.

v2.2.0

New features:

• Added vertical-expanded property to allow vertical px-app-nav instances to be permanently expanded (thanks @nayanchandni)

Bug fixes

• Fixed missing drop shadow on sub navigation

Polymer 1.x/2.x hybrid element support

v2.1.0

Design Refresh

v2.0.0

made icons available in shadow dom

Icons now show up in shadow dom mode.

added auto github pages functionality

v1.5.2

added auto github pages functionality