Add 'objectValues' JS util function

[IvanGoncharov]

Following pattern are frequently used in this lib:

const objMap = ...
Object.keys(objMap).map(name => {
  const item = objMap[name];
  // ...
})

It can be greatly simplify with Object.values however Flow can't hadle it well and IE doesn't implement it.
This PR adds objectValues substitution to use until we could switch to Object.values.

Plus it should give small performance boost from using native Object.values when possible.