Positioning, Event Binding and Space event selection, oh my!

This update fixes some position issues on mobile-size device screens of the menu as well as introduces some new configuration options.

• Correctly position menu on mobile devices with limited screen real estate. #177 Thank you @fynnfeldpausch!
• Use mouseup instead of mousedown for event binding. #176 Thank you again @fynnfeldpausch!
• Return mention text in lookup when lookup is a function. 3e805c5

lookup: function (item, mentionText) {
 ...
}

• Add support for selecting match when spacebar is pressed. This is disabled by default and can been enabled by setting spaceSelectsMatch to true in your config. 994fbf2 Thank you @htmltiger for the suggestion.

Thank you to everyone who contributed to this release!