Modifier key queries

Inspired by keymaster.
This is a small subset of the functionality in that library. See for yourself how small it is.

At any point in time you can query the modifiers object to see if a modifier key is held down.

Default supported keys are:
shift, alt, option (same as alt), control, command

``javascript
if (modifiers.command || modifiers.control) {
// do something special
}

// ..inside your click handler
if (modifiers.shift) {
...
}
`

You can also add your own to the defaults:
`javascript
modifiers.add({{
leftArrow: 37,
upArrow: 38,
rightArrow: 39,
downArrow: 40,
w: 87,
a: 65,
s: 83,
d: 68
});
`

$3

To create the minified and compressed version with source mapping, run:

uglifyjs modifiers.js --source-map modifiers.min.map --screw-ie8 -c -m -o modifiers.min.js`

The code uses addEventListener so if you sadly need to support IE8 you'll want to change the code to use
something like what's described here.

$3

MIT