### call

Given a key and a set of arguments, call them when given a context. Primarily useful in composition.

Use a closure to call a stored key with stored arguments.

```js
const call = ( key, ...args ) => context => context[ key ]( ...args );
/*
Promise.resolve( [ 1, 2, 3 ] ).then( call('map', x => 2 * x ) ).then( console.log ) //[ 2, 4, 6 ]
const map = call.bind(null, 'map')
Promise.resolve( [ 1, 2, 3 ] ).then( map( x => 2 * x ) ).then( console.log ) //[ 2, 4, 6 ]
*/
```