Extract imports from variable declarations

[eventualbuddha]

For example:

var d        = require('d')
  , callable = require('es5-ext/object/valid-callable')

  , apply = Function.prototype.apply, call = Function.prototype.call;

We should remove them from the variable declaration, and remove the whole variable declaration if it wouldn't have any declarators:

import d from 'd';
import callable from 'es5-ext/object/valid-callable';
var apply = Function.prototype.apply, call = Function.prototype.call;