Add object arguments form for spread method

[sergeysova]

// Before
spread(formReceived, {
  first: $first,
  last: $last,
});

const source = spread({
  first: $first,
  last: $last,
});

// NOW
spread({
  source: formReceived,
  targets: {
    first: $first,
    last: $last,
  },
});

const source = spread({
  targets: {
    first: $first,
    last: $last,
  },
});

BREAKING CHANGE: removed spread(source, targets) and source = spread(targets)

Closes #45
Closes #4